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                                                                     Exhibit 4.5

                             REGISTRATION AGREEMENT

      THIS AGREEMENT is made as of February 10, 2005, among Emergency Medical
Services L.P., a Delaware limited partnership (the "COMPANY"), and the Persons
listed on Schedule A attached hereto and such other equityholders of the Company
as may, from time to time, become parties to this Agreement in accordance with
the provisions hereof (the "INVESTORS").

      Upon consummation of (i) the Stock Purchase Agreement, dated as of
December 6, 2004, by and among Laidlaw International, Inc., Laidlaw Medical
Holdings, Inc. and EMSC, Inc. with respect to the acquisition of the common
stock of EmCare Holdings Inc., (ii) the Stock Purchase Agreement, dated as of
December 6, 2004, by and among Laidlaw International, Inc., Laidlaw Medical
Holdings, Inc. and EMSC, Inc. with respect to the acquisition of the common
stock of American Medical Response, Inc., and of certain related transactions to
be consummated concurrently therewith, Onex Partners and certain other
equityholders will own or may hereafter acquire units representing limited
partnership interests in the Company (the "UNITS"). In order to induce Investors
to purchase Units by subscription, through the exercise of options or otherwise
the Company has agreed to provide the registration rights set forth in this
Agreement.

      The parties, intending to be legally bound hereby, agree as follows:

      1.    Demand Registrations.

            (a)   Requests for Registration. Subject to Sections 1(b) and 1(c),
at any time after the Reorganization Date, the Majority Onex Investors may
request registration under the Securities Act of all or part of their
Registrable Securities on Form S-1 or any similar long-form registration
("LONG-FORM REGISTRATIONS") or, if available, on Form S-2 or S-3 or any similar
short-form registration ("SHORT-FORM REGISTRATIONS"). In addition, at any time
after the consummation of a Public Offering, the holders of a majority of the
Registrable Securities may request Long-Form Registrations or, if available,
Short-Form Registrations of all or part of their Registrable Securities until
such holders cease to hold at least 10% of the number of Registrable Securities
held by such holders as of the date hereof. Each request for a registration
under this Section 1(a) shall specify the approximate number of Registrable
Securities requested to be registered and the proposed method of distribution.
Within ten days after receipt of any such request, the Company will give written
notice of such requested registration to all other holders of Registrable
Securities and, subject to Section 1(d), will include in such registration all
Registrable Securities with respect to which the Company has received written
requests for inclusion therein within 15 days after the receipt of the Company's
notice. All registrations requested pursuant to this Section 1(a) are referred
to herein as "DEMAND REGISTRATIONS."

            (b)   Long-Form Registrations. The holders of a majority of the
Registrable Securities will be entitled to request three Long-Form Registrations
in which the Company will pay all Registration Expenses and the Majority Onex
Investors will be entitled to request an unlimited number of Long-Form
Registrations in which the Company will pay all Registration Expenses
("COMPANY-PAID LONG-FORM REGISTRATIONS"). A registration will not count as one
of the permitted Long-Form Registrations until it has become effective (unless
such Long-Form Registration has not become effective due solely to the fault of
the holders requesting such registration and such holders

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do not agree to bear all Registration Expenses in connection therewith);
provided, that in any event (absent such an agreement by the holders requesting
such registration) the Company will pay all Registration Expenses in connection
with any registration initiated as a Company-Paid Long-Form Registration whether
or not it has become effective. All Long-Form Registrations shall be
underwritten registrations.

            (c)   Short-Form Registrations. In addition to the Company-Paid
Long-Form Registrations provided pursuant to Section 1(b), the Majority Onex
Investors and the holders a majority of the Registrable Securities will each be
entitled to request an unlimited number of Short-Form Registrations in which the
Company will pay all Registration Expenses. Demand Registrations will be
Short-Form Registrations whenever the Company is permitted to use any applicable
short form. After the Company has become subject to the reporting requirements
of the Securities Exchange Act, the Company will use its commercially reasonable
efforts to be eligible to use Short-Form Registrations for the sale of
Registrable Securities.

            (d)   Priority on Demand Registrations. The Company will not include
in any Demand Registration any securities that are not Registrable Securities
without the prior written consent of the holders of at least a majority of the
Registrable Securities included in such registration. If a Demand Registration
is an underwritten offering and the managing underwriters advise the Company in
writing that in their opinion the number of Registrable Securities and, if
permitted pursuant to the immediately preceding sentence, other securities
requested to be included in such offering exceeds the number of Registrable
Securities and other securities, if any, which can be sold therein without
adversely affecting the marketability of the offering, the Company will include
in such registration prior to the inclusion of any securities which are not
Registrable Securities the number of Registrable Securities requested to be
included (whether upon exercise of a demand registration right or upon exercise
of the right to participate in such a demand registration) that in the opinion
of such underwriters can be sold without adversely affecting the marketability
of the offering, pro rata among the respective holders thereof on the basis of
the number of Registrable Securities requested to be included by each such
holder.

            (e)   Restrictions on Demand Registrations. The Company will not be
obligated to effect any Demand Registration within six months after the
effective date of a Demand Registration or a registration in which the holders
of Registrable Securities were given piggyback rights pursuant to Section 2 and
in which there was no reduction in the number of Registrable Securities
requested to be included. The Company may postpone for up to six months the
filing or the effectiveness of a registration statement for a Demand
Registration if the Board of Directors of the Company determines that such
Demand Registration would reasonably be expected to have an adverse effect on
(i) any proposal or plan by the Company or any of its subsidiaries to engage in
any acquisition of assets (other than in the ordinary course of business) or any
merger, consolidation, tender offer or similar transaction, or (ii) any material
corporate development; provided that in such event, the holders of Registrable
Securities initially requesting such Demand Registration will be entitled to
withdraw such request and, if such request is withdrawn, such Demand
Registration will not count as a requested Demand Registrations hereunder and
the Company will pay all Registration Expenses in connection with such
registration.

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            (f)   Selection of Underwriters. The holders of a majority of the
Registrable Securities included in any Demand Registration will have the right
to select the investment banker(s) and manager(s) to administer the offering,
subject to the Company's approval which will not be unreasonably withheld.

            (g)   Other Registration Rights. The Company will not grant to any
Persons the right to request the Company to register any equity securities of
the Company, or any securities convertible or exchangeable into or exercisable
for such securities, without the prior written consent of the holders of at
least a majority of the Registrable Securities; provided, that the Company may
grant rights to other Persons to participate in Piggyback Registrations or
Demand Registrations so long as such rights are subordinate to the rights of the
holders of Registrable Securities with respect to such Piggyback Registrations
or Demand Registrations.

      2.    Piggyback Registrations.

            (a)   Right to Piggyback. Whenever the Company proposes to register
any of its securities under the Securities Act (including primary registrations
on behalf of the Company and secondary registrations on behalf of the holders of
its securities other than pursuant to a Demand Registration) and the
registration form to be used may be used for the registration of Registrable
Securities (a "PIGGYBACK REGISTRATION"), the Company will give prompt written
notice to all holders of Registrable Securities of its intention to effect such
a registration and will include in such registration all Registrable Securities
with respect to which the Company has received written requests for inclusion
therein within 15 days after the receipt of the Company's notice.

            (b)   Piggyback Expenses. The Registration Expenses of the holders
of Registrable Securities will be paid by the Company in all Piggyback
Registrations.

            (c)   Priority on Primary Registrations. If a Piggyback Registration
is an underwritten primary registration on behalf of the Company, and the
managing underwriters advise the Company in writing that in their opinion the
number of securities requested to be included in such registration exceeds the
number which can be sold in such offering without adversely affecting the
marketability of the offering, the Company will include in such registration (i)
first, the securities the Company proposes to sell, (ii) second, the Registrable
Securities requested to be included in such registration, pro rata among the
holders of such Registrable Securities on the basis of the number of shares
requested to be included by each such holder, and (iii) third, other securities
requested to be included in such registration.

            (d)   Priority on Secondary Registrations. If a Piggyback
Registration is an underwritten secondary registration on behalf of holders of
the Company's securities, and the managing underwriters advise the Company in
writing that in their opinion the number of securities requested to be included
in such registration exceeds the number which can be sold in such offering
without adversely affecting the marketability of the offering, the Company will
include in such registration (i) first, pro rata among the securities requested
to be included therein by the holders requesting such registration and the other
Registrable Securities requested to be included in such registration, on the
basis of the number of shares requested to be included by each such holder, and
(ii) second, other securities requested to be included in such registration.

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            (e)   Selection of Underwriters. If any Piggyback Registration is an
underwritten offering, the selection of investment banker(s) and manager(s) for
the offering must be approved by the holders of a majority of the Registrable
Securities included in such Piggyback Registration. Such approval will not be
unreasonably withheld.

            (f)   Other Registrations. If the Company has previously filed a
registration statement with respect to Registrable Securities pursuant to
Section 1 or pursuant to this Section 2, and if such previous registration has
not been withdrawn or abandoned, the Company will not, except as required by
Section 1, file or cause to be effected any other registration of any of its
equity securities or securities convertible or exchangeable into or exercisable
for its equity securities under the Securities Act (except on Form S-8 or Form
S-4 or any successor forms), whether on its own behalf or at the request of any
holder or holders of such securities, until a period of at least six months has
elapsed from the effective date of such previous registration.

      3.    Holdback Agreements.

            (a)   Each holder of Registrable Securities agrees not to effect any
public sale or distribution (including sales pursuant to Rule 144 under the
Securities Act) of Registrable Securities of the Company, or any securities
convertible into or exchangeable or exercisable for such securities, during the
seven days prior to and the 90-day (180-day in the case of the initial Public
Offering) period beginning on the effective date of any underwritten Demand
Registration or any underwritten Piggyback Registration in which Registrable
Securities are included or which is the initial Public Offering (except as part
of such underwritten registration), unless the underwriters managing the
registered public offering otherwise agree.

            (b)   The Company agrees (i) not to effect any public sale or
distribution of its equity securities, or any securities convertible into or
exchangeable or exercisable for such securities, during the seven days prior to
and during the 90-day period beginning on the effective date of any underwritten
Demand Registration or any underwritten Piggyback Registration (except as part
of such underwritten registration or pursuant to registrations on Form S-8 or
S-4 or any successor form), unless the underwriters managing the registered
public offering otherwise agree, and (ii) to cause each holder of its common
stock, or any securities convertible into or exchangeable or exercisable for
common stock, purchased from the Company at any time after the date of this
Agreement (other than in a registered public offering) to agree not to effect
any public sale or distribution (including sales pursuant to Rule 144 under the
Securities Act) of any Registrable Securities during such period (except as part
of such underwritten registration, if otherwise permitted), unless the
underwriters managing the registered public offering otherwise agree.

      4.    Registration Procedures. Whenever the holders of Registrable
Securities have requested that any Registrable Securities be registered pursuant
to this Agreement, the Company will use commercially reasonable efforts to
effect the registration and the sale of such Registrable Securities in
accordance with the intended method of disposition thereof, and pursuant thereto
the Company will as expeditiously as possible:

            (a)   prepare and file with the Securities and Exchange Commission a
registration statement with respect to such Registrable Securities and use its
commercially reasonable efforts to cause such registration statement to become
effective (provided that, before filing a registration

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statement or prospectus or any amendments or supplements thereto, the Company
will furnish to the counsel selected by the holders of a majority of the
Registrable Securities covered by such registration statement copies of all such
documents proposed to be filed, which documents will be subject to the review of
such counsel);

            (b)   prepare and file with the Securities and Exchange Commission
such amendments and supplements to such registration statement and the
prospectus used in connection therewith as may be necessary to keep such
registration statement effective for the period required to accomplish the plan
of distribution set forth therein (but not more than six months) and comply with
the provisions of the Securities Act with respect to the disposition of all
securities covered by such registration statement during such period in
accordance with the intended methods of disposition by the sellers thereof set
forth in such registration statement;

            (c)   furnish to each seller of Registrable Securities such number
of copies of such registration statement, each amendment and supplement thereto,
the prospectus included in such registration statement (including each
preliminary prospectus) and such other documents as such seller may reasonably
request in order to facilitate the disposition of the Registrable Securities
owned by such seller;

            (d)   use its commercially reasonable efforts to register or qualify
such Registrable Securities under such other securities or blue sky laws of such
jurisdictions as any seller reasonably requests and do any and all other acts
and things which may be reasonably necessary or advisable to enable such seller
to consummate the disposition in such jurisdictions of the Registrable
Securities owned by such seller (provided, that the Company will not be required
to (i) qualify generally to do business in any jurisdiction, (ii) subject itself
to taxation in any such jurisdiction or (iii) consent to general service of
process in any such jurisdiction, in each case where it would not otherwise be
required to qualify, subject itself to taxation or consent to general service of
process but for this subparagraph);

            (e)   notify each seller of such Registrable Securities, at any time
when a prospectus relating thereto is required to be delivered under the
Securities Act, of the happening of any event as a result of which the
prospectus included in such registration statement contains an untrue statement
of a material fact or omits any fact necessary to make the statements therein
not misleading, and, at the request of any such seller, the Company will
promptly prepare a supplement or amendment to such prospectus so that, as
thereafter delivered to the purchasers of such Registrable Securities, such
prospectus will not contain an untrue statement of a material fact or omit to
state any fact necessary to make the statements therein not misleading;

            (f)   cause all such Registrable Securities to be listed on each
securities exchange on which similar securities issued by the Company are then
listed and, if not so listed, to be listed, if eligible for such listing, on one
or more securities exchanges or the NASD automated quotation system (on the
National Market System if the Company so qualifies);

            (g)   provide a transfer agent and registrar for all such
Registrable Securities not later than the effective date of such registration
statement;

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            (h)   enter into such customary agreements (including underwriting
agreements in customary form) and take all such other actions as the
underwriters reasonably request in order to expedite or facilitate the
disposition of such Registrable Securities (including, without limitation,
effecting a stock split or a combination of shares);

            (i)   make available for inspection by any seller of Registrable
Securities, any underwriter participating in any disposition pursuant to such
registration statement and any attorney, accountant or other agent retained by
any such seller or underwriter, all financial and other records, pertinent
corporate documents and properties of the Company, and cause the Company's
officers, directors, employees and independent accountants to supply all
information reasonably requested by any such seller, underwriter, attorney,
accountant or agent in connection with such registration statement;

            (j)   otherwise use its commercially reasonable efforts to comply
with all applicable rules and regulations of the Securities and Exchange
Commission, and make available to its security holders, as soon as reasonably
practicable, an earnings statement covering the period of at least twelve months
beginning with the first day of the Company's first full calendar quarter after
the effective date of the registration statement, which earnings statement shall
satisfy the provisions of Section 11(a) of the Securities Act and Rule 158
thereunder;

            (k)   in the event of the issuance of any stop order suspending the
effectiveness of a registration statement, or of any order suspending or
preventing the use of any related prospectus or suspending the qualification of
any common stock included in such registration statement for sale in any
jurisdiction, the Company will use its reasonable best efforts promptly to
obtain the withdrawal of such order;

            (l)   obtain comfort letters, dated (i) the effective date of such
registration statement, (ii) the date the Registrable Securities being sold are
delivered to the underwriters, if any, for sale pursuant thereto and (iii) if
required by the underwriters, if any, on or prior to the date of any preliminary
prospectuses, from the Company's independent public accountants in customary
form and covering such matters of the type customarily covered by comfort
letters and if the Registrable Securities included in such registration
statement constitute at least 10% of the securities covered by such registration
statement, also covering such matters as the holders of a majority of the
Registrable Securities being sold reasonably request;

            (m)   provide a legal opinion of the Company's outside counsel with
respect to the registration statement, each amendment and supplement thereto,
the prospectus included therein (including the preliminary prospectus) and such
other documents relating thereto in customary form and covering such matters of
the type customarily covered by legal opinions of such nature;

            (n)   if requested by the managing underwriter or underwriters or a
holder of Registrable Securities being sold in connection with an underwritten
offering, promptly incorporate in a prospectus supplement or post-effective
amendment such information as the managing underwriters and the holders of a
majority of the Registrable Securities being sold agree should be included
therein relating to the plan of distribution with respect to such Registrable
Securities, including, without limitation, information with respect to the
number of Registrable Securities being sold to such underwriters, the purchase
price being paid therefor by such underwriters and with

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respect to any other terms of the underwritten (or best efforts underwritten)
offering of the Registrable Securities to be sold in such offering; and make all
required filings of such prospectus supplement or post-effective amendment as
soon as notified of the matters to be incorporated in such prospectus supplement
or post-effective amendment;

            (o)   cooperate with the selling holders of Registrable Securities
and the managing underwriters, if any, to facilitate the timely preparation and
delivery of certificates representing Registrable Securities to be sold and not
bearing any restrictive legends; and enable such Registrable Securities to be in
such denominations and registered in such names as the managing underwriters may
request at least two business days prior to any sale of Registrable Securities
to the underwriters;

            (p)   cooperate with, and make members of management available to
participate in, road shows and other marketing activities as reasonably
requested by the managing underwriter or underwriters; and

            (q)   use its commercially reasonable efforts to cause the
Registrable Securities covered by the applicable registration statement to be
registered with or approved by such other governmental agencies or authorities
as may be necessary to enable the seller or sellers thereof or the underwriters,
if any, to consummate the disposition of such Registrable Securities.

      5.    Registration Expenses.

            (a)   All expenses incident to the Company's performance of or
compliance with this Agreement, including, without limitation, all registration
and filing fees, fees and expenses associated with filings required to be made
with the NASD (including, if applicable, the fees and expenses of any "qualified
independent underwriter"and its counsel as may be required by the rules and
regulations of the NASD), fees and expenses of compliance with securities or
blue sky laws, printing expenses, messenger and delivery expenses and fees and
disbursements of counsel for the Company and all independent certified public
accountants, underwriters (excluding discounts and commissions) and other
Persons retained by the Company (all such expenses being herein called
"REGISTRATION EXPENSES"), will be borne as provided in this Agreement, except
that the Company will, in any event, pay its internal expenses (including,
without limitation, all salaries and expenses of its officers and employees
performing legal or accounting duties), the expense of any annual audit or
quarterly review, the expense of any liability insurance and the expenses and
fees for listing the securities to be registered on each securities exchange on
which similar securities issued by the Company are then listed or on the NASD
automated quotation system (on the National Market System if the Company so
qualifies).

            (b)   In connection with each Demand Registration and each Piggyback
Registration, the Company will reimburse the holders of Registrable Securities
covered by such registration for the reasonable fees and disbursements of one
counsel chosen by the holders of a majority of the Registrable Securities
initially requesting such registration (in the case of a Demand Registration) or
the holders of a majority of the Registrable Securities included in such
registration (in the case of a Piggyback Registration).

            (c)   To the extent Registration Expenses are not required to be
paid by the Company, each holder of securities included in any registration
hereunder will pay those Registration

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Expenses allocable to the registration of such holder's securities so included,
and any Registration Expenses not so allocable will be borne by all sellers of
securities included in such registration in proportion to the aggregate selling
price of the securities to be so registered.

      6.    Indemnification.

            (a)   The Company agrees to indemnify, to the extent permitted by
law, each holder of Registrable Securities, its officers and directors and each
Person who controls such holder (within the meaning of the Securities Act or the
Securities Exchange Act) against all losses, claims, damages, liabilities and
expenses (including any amounts paid in any settlement effected with the
Company's consent, which consent shall not be unreasonably withheld) caused by
any untrue or alleged untrue statement of material fact contained in any
registration statement, prospectus or preliminary prospectus or any amendment
thereof or supplement thereto or any omission or alleged omission of a material
fact required to be stated therein or necessary to make the statements therein
not misleading or any violation by the Company of any federal, state or common
law risk applicable to the Company and relating to action required of or
inaction by the Company in connection with such registration, except insofar as
the same are caused by or contained in any information furnished in writing to
the Company by such holder expressly for use therein or by such holder's failure
to deliver a copy of the registration statement or prospectus or any amendments
or supplements thereto after the Company has furnished such holder with a
sufficient number of copies of the same. In connection with an underwritten
offering, the Company will indemnify such underwriters, their officers and
directors and each Person who controls such underwriters (within the meaning of
the Securities Act or the Securities Exchange Act) to the same extent as
provided above with respect to the indemnification of the holders of Registrable
Securities.

            (b)   In connection with any registration statement in which a
holder of Registrable Securities is participating, each such holder will furnish
to the Company in writing such information relating to such holder and its
Registrable Securities as the Company reasonably requests for use in connection
with any such registration statement or prospectus and, to the extent permitted
by law, will indemnify the Company, its directors and officers and each Person
who controls the Company (within the meaning of the Securities Act or the
Securities Exchange Act) against any losses, claims, damages, liabilities and
expenses resulting from any untrue or alleged untrue statement of material fact
contained in the registration statement, prospectus or preliminary prospectus or
any amendment thereof or supplement thereto or any omission or alleged omission
of a material fact required to be stated therein or necessary to make the
statements therein not misleading, but only to the extent that such untrue
statement or omission is contained in any information or affidavit so furnished
in writing by such holder which specifically states that it is for use in the
preparation of such registration statement, prospectus or preliminary prospectus
or any amendment thereof or supplement thereto; provided that the obligation to
indemnify will be individual to each holder and will be limited to the net
amount of proceeds received by such holder from the sale of Registrable
Securities pursuant to such registration statement.

            (c)   Any Person entitled to indemnification hereunder will (i) give
prompt written notice to the indemnifying party of any claim with respect to
which it seeks indemnification (but any failure to so notify the indemnifying
party shall not relieve it of any liability which it may otherwise have to any
indemnified party unless such failure shall materially adversely affect the
defense of such

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claim) and (ii) unless in such indemnified party's reasonable judgment a
conflict of interest between such indemnified and indemnifying parties may exist
with respect to such claim, permit such indemnifying party to assume the defense
of such claim with counsel reasonably satisfactory to the indemnified party. If
such defense is assumed, the indemnifying party will not be subject to any
liability for any settlement made by the indemnified party without its consent
(but such consent will not be unreasonably withheld). An indemnifying party who
is not entitled to, or elects not to, assume the defense of a claim will not be
obligated to pay the fees and expenses of more than one counsel for all parties
indemnified by such indemnifying party with respect to such claim, unless in the
reasonable judgment of any indemnified party a conflict of interest may exist
between such indemnified party and any other of such indemnified parties with
respect to such claim.

            (d)   The indemnification provided for under this Agreement will
remain in full force and effect regardless of any investigation made by or on
behalf of the indemnified party or any officer, director or controlling Person
of such indemnified party and will survive the transfer of securities. The
Company also agrees to make such provisions, as are reasonably requested by any
indemnified party, for contribution to such party in such proportion as is
appropriate to reflect the relative benefits received by, and the relative fault
of, the Company and such indemnified party in the event the Company's
indemnification is unavailable for any reason. The indemnification and
contribution provided for in this Agreement shall be in addition to, and not in
lieu of, the indemnification and contribution provisions in any underwriting or
similar agreement.

      7.    Participation in Registrations.

            (a)   No Person may participate in any registration hereunder which
is underwritten unless such Person (i) agrees to sell such Person's securities
on the basis provided in any underwriting arrangements approved by the Person or
Persons entitled hereunder to approve such arrangements (including, without
limitation, pursuant to the terms of any over-allotment or "green shoe" option
requested by the managing underwriter(s)) and (ii) completes and executes all
questionnaires, powers of attorney, indemnities, underwriting agreements and
other documents reasonably required under the terms of such underwriting
arrangements.

            (b)   Each Person that is participating in any registration
hereunder agrees that, upon receipt of any notice from the Company of the
happening of any event of the kind described in Section 4(e), such Person will
forthwith discontinue the disposition of its Registrable Securities pursuant to
the registration statement until such Person's receipt of the copies of a
supplemented or amended prospectus as contemplated by Section 4(e).

      8.    Current Public Information. At all times after the Company has
effected a Public Offering, the Company will use commercially reasonable efforts
to file all reports required to be filed by it under the Securities Act and the
Securities Exchange Act and the rules and regulations adopted by the Securities
and Exchange Commission thereunder, and will take such further action as any
holder or holders of Registrable Securities may reasonably request, all to the
extent required to enable such holders to sell Registrable Securities pursuant
to Rule 144 adopted by the Securities and Exchange commission under the
Securities Act (as such rule may be amended from time to time) or any similar
rule or regulation hereafter adopted by the Securities and Exchange Commission.

      9.    Definitions.

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            (a)   "COMMON STOCK" means the Company's common stock.

            (b)   "COMPANY" includes any successor to the Company resulting from
any merger, consolidation or other reorganization of or including the Company.

            (c)   "EQUITYHOLDERS AGREEMENT" means the Investor Equityholders
Agreement, of even date herewith, entered into by and among the Company and the
Investors.

            (d)   "PERSON" means an individual, a partnership, a joint venture,
a corporation, a limited liability company, a trust, an unincorporated
organization or a government or any department or agency thereof.

            (e)   "PUBLIC OFFERING" means the sale in an underwritten public
offering under the Securities Act of equity securities of the Company.

            (f)   "PUBLIC SALE" means any sale of the Company's common stock to
the public pursuant to an offering registered under the Securities Act or to the
public through a broker, dealer or to a market maker pursuant to the provisions
of Rule 144 adopted under the Securities Act.

            (g)   "REGISTRABLE SECURITIES" means (i) any Common Stock issued in
exchange for Units issued and outstanding as of the date hereof, (ii) any Common
Stock issued in exchange for Units issued upon the exercise of options granted
pursuant to the Emergency Medical Services L.P. Equity Option Plan, (iii) any of
the Company's common stock issued or issuable with respect to the securities
referred to in clause (i) or (ii) by way of a stock dividend or stock split or
in connection with a combination of shares, recapitalization, merger,
consolidation or other reorganization, and (iv) any other shares of the
Company's common stock held by Persons holding securities described in clauses
(i), (ii) or (iii). As to any particular Registrable Securities, such securities
will cease to be Registrable Securities when they have been sold pursuant to a
Public Sale. For purposes of this Agreement, a Person will be deemed to be a
holder of Registrable Securities whenever such Person has the right to acquire
directly or indirectly such Registrable Securities (upon conversion, exchange or
exercise in connection with a transfer of securities or otherwise, but
disregarding any restrictions or limitations upon the exercise of such right),
whether or not such acquisition has actually been effected.

            (h)   "REGISTRATION EXPENSES" has the meaning set forth in Section
5(a).

            (i)   "REORGANIZATION DATE" means the date on which the Company, as
a limited partnership, engages in a merger, consolidation or other
reorganization in which the successor is a corporation and the Units are
exchanged for other equity securities of the Company.

            (j)   "SECURITIES ACT" means the Securities Act of 1933, as amended,
or any similar federal law then in force.

            (k)   "SECURITIES AND EXCHANGE COMMISSION" includes any governmental
body or agency succeeding to the functions thereof.

                                       10

<PAGE>

            (l)   "SECURITIES EXCHANGE ACT" means the Securities Exchange Act of
1934, as amended, or any similar federal law then in force.

            (m)   "UNITS" includes any Units issued or issuable by way of a
dividend or split or in connection with a combination of Units,
recapitalization, merger, consolidation or other reorganization.

Unless otherwise stated, other capitalized terms contained herein have the
meanings set forth in the Equityholders Agreement.

      10.   Miscellaneous.

            (a)   No Inconsistent Agreements. The Company will not hereafter
enter into any agreement with respect to its securities which is inconsistent
with or violates the rights granted to the holders of Registrable Securities in
this Agreement.

            (b)   Remedies. The parties shall be entitled to enforce their
rights under this Agreement specifically to recover damages by reason of any
breach of any provision of this Agreement and to exercise all other rights
existing in their favor. The parties hereto agree and acknowledge that money
damages may not be an adequate remedy for any breach of the provisions of this
Agreement and that any party may in its sole discretion apply to any court of
law or equity of competent jurisdiction for specific performance and/or
temporary, preliminary or permanent injunctive relief (without posting a bond or
other security) in order to enforce or prevent any violation of the provisions
of this Agreement.

            (c)   Amendments and Waivers. Except as otherwise provided herein,
the provisions of this Agreement may be amended or waived only upon the prior
written consent of the Company, the Majority Onex Investors and the holders of
at least a majority of the Registrable Securities. The failure of a party to
insist upon strict adherence to any term of this Agreement on any occasion shall
not be considered a waiver or deprive that party of the right thereafter to
insist upon strict adherence to that term or any other term of this Agreement.
No purported waiver shall be effective unless in writing. The waiver by any
party of a breach of any provision of this Agreement shall not operate or be
construed as a waiver of any subsequent or other breach.

            (d)   Successors and Assigns. All covenants and agreements in this
Agreement by or on behalf of any of the parties hereto will bind and inure to
the benefit of the respective successors and assigns of the parties hereto
whether so expressed or not. In addition, whether or not any express assignment
has been made, the provisions of this Agreement which are for the benefit of
purchasers or holders of Registrable Securities are also for the benefit of, and
enforceable by, any subsequent holder of Registrable Securities who agrees to be
bound by the provisions of this Agreement.

            (e)   Severability. If any provision of this Agreement is held
invalid or unenforceable by any court of competent jurisdiction, the other
provisions of this Agreement will remain in full force and effect. Any
provisions of this Agreement held invalid or unenforceable only in part or
degree will remain in full force and effect to the extent not held invalid or
unenforceable.

                                       11

<PAGE>

            (f)   Counterparts; Joinder. This Agreement may be executed in
counterparts, each of which shall be considered an original, but all of which
together shall constitute one and the same instrument. Additional Persons may
become parties to this Agreement as "Investors" with the consent of the Company
and the Majority Onex Investors, by executing and delivering to the Company a
joinder agreement.

            (g)   Interpretation. In this Agreement, unless a contrary intention
appears, (i) the words "herein," "hereof" and "hereunder" and other words of
similar import refer to this Agreement as a whole and not to any particular
Section or other subdivision, (ii) the words "include," "includes" or
"including" shall be deemed to be followed by the words "without limitation,"
(iii) reference to any Section means such Section hereof, (iv) words of any
gender shall be deemed to include each other gender, and (v) words using the
singular or plural number shall also include the plural or singular number,
respectively. No provision of this Agreement shall be interpreted or construed
against any party hereto solely because such party or its legal representative
drafted such provision.

            (h)   Captions. The captions in this Agreement are for convenience
of reference only and shall not be given any effect in the interpretation of
this Agreement.

            (i)   Governing Law. This Agreement shall be construed in accordance
with, and governed by, the laws of the State of Delaware without regard to
conflicts of laws principles which would result in the application of the laws
of another jurisdiction.

            (j)   Jurisdiction. The parties hereby irrevocably and
unconditionally consent to submit to the exclusive jurisdiction of the courts of
the State of Delaware and the United States District Court for the District of
Delaware for any actions, suits or proceedings arising out of or relating to
this agreement and the transactions contemplated hereby (and agree not to
commence any action, suit or proceeding relating thereto except in such courts).
The parties hereby irrevocably and unconditionally waive any objection to the
laying of venue of any action, suit or proceeding arising out of this Agreement
or the transactions contemplated hereby in the courts of the State of Delaware
and the United States District Court from the District of Delaware, and hereby
further irrevocably and unconditionally waive and agree not to plead or claim in
any such court that any such action, suit or proceeding brought in any such
court has been brought in an inconvenient forum.

            (k)   Waiver of Jury Trial. EACH OF THE PARTIES HERETO IRREVOCABLY
WAIVES ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING ARISING OUT OF
OR RELATED TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY.

            (l)   Complete Agreement. This Agreement, the documents expressly
referred to herein and other documents of even date herewith embody the complete
agreement and understanding among the parties and supersede and preempt any
prior understanding, agreements or representations by or among the parties,
written or oral, that may be related to the subject matter hereof in any way.

            (m)   Notices. All notices, consents and other communications
required or permitted to be given under or by reason of this Agreement shall be
in writing, shall be delivered personally or by e-mail or telecopy as described
below or by reputable overnight courier, and shall be

                                       12

<PAGE>

deemed given on the date on which such delivery is made, provided, that any such
delivery made on a day that is not a Business Day, or that is made after 5:00
p.m. on a Business Day, shall be deemed to have been given on the following
Business Day. If delivered by e-mail or telecopy, such notices or communications
shall be confirmed by a registered or certified letter (return receipt
requested), postage prepaid. Such notices, consents and other communications
will be sent to the parties at the addresses specified for notices in the
Equityholders Agreement or to such other address as the recipient has specified
by prior notice to the other parties.

                            [Signature Pages Follow]

                                       13

<PAGE>

      IN WITNESS WHEREOF, this Registration Agreement has been duly executed by
the parties hereto, all as of the date first above written.

                        EMERGENCY MEDICAL SERVICES L.P.

                        By:  Emergency Medical Services Corporation, its general
                             partner

                        By:     /s/ Robert M. Le Blanc
                            ----------------------------------------
                            Name:  Robert M. Le Blanc
                            Title: President

                   [Signature Page to Registration Agreement]

<PAGE>

      IN WITNESS WHEREOF, this Registration Agreement has been duly executed by
the parties hereto, all as of the date first above written.

                        ONEX AMERICAN HOLDINGS II LLC

                        By: /s/ Donald F. West
                            ----------------------------------------------------
                            Name: Donald F. West
                            Title: Director

                        By: /s/ Eric J. Rosen
                            ----------------------------------------------------
                            Name: Eric J. Rosen
                            Title: Director

                        ONEX US PRINCIPALS LP

                        By: Onex American Holdings GP LLC, its General Partner

                        By: /s/ Donald F. West
                            ----------------------------------------------------
                            Name: Donald F. West
                            Title: Representative

                        EMS EXECUTIVE INVESTCO LLC

                        By: /s/ Donald F. West
                            ----------------------------------------------------
                            Name: Donald F. West
                            Title:

[Signature Page to Registration Agreement]


<PAGE>
                        ONEX EMSC CO-INVEST LP



                        By: Onex Partners GP LP, its General Partner
                        By: Onex Partners Manager LP, its Agent
                        By: Onex Partners Manager GP Inc., its General Partner

                        By: /s/ Robert M. Le Blanc
                            ------------------------------------
                            Name: Robert M. Le Blanc
                            Title: Managing Director

                        By: /s/ Eric J. Rosen
                            ------------------------------------
                            Name: Eric J. Rosen
                            Title: Managing Director

                        ONEX PARTNERS LP

                        By: Onex Partners GP LP, its General Partner
                        By: Onex Partners Manager LP, its Agent
                        By: Onex Partners Manager GP Inc., its General Partner

                        By: /s/ Robert M. Le Blanc
                            -----------------------------------
                            Name: Robert M. Le Blanc
                            Title: Managing Director

                        By: /s/ Eric J. Rosen
                            -----------------------------------
                            Name: Eric J. Rosen
                            Title: Managing Director

                   [Signature Page to Registration Agreement]

<PAGE>

      IN WITNESS WHEREOF, this Registration Agreement has been duly executed by
the undersigned.

Dated: __March 11, 2005__

                                    INVESTOR

                                        /s/ Colby Bartlett LLC
                                    -----------------------------
                                    Name: Colby Bartlett LLC
                                            Robert Haft, Manager

       [Signature page (joinder agreement) to the Registration Agreement]

<PAGE>

      IN WITNESS WHEREOF, this Registration Agreement has been duly executed by
the undersigned.

Dated: March 11, 2005__

                                    INVESTOR

                                      /s/ Steven Shulman
                                    -----------------------
                                    Name: Steven Shulman

       [Signature page (joinder agreement) to the Registration Agreement]

<PAGE>

      IN WITNESS WHEREOF, this Registration Agreement has been duly executed by
the parties hereto, all as of the date first above written.

                                    INVESTOR

                                          /s/ Angel L. Iscovich
                                    ----------------------------------

                                    Name: Angel L. Iscovich

                 [Signature page to the Registration Agreement]

<PAGE>

      IN WITNESS WHEREOF, this Registration Agreement has been duly executed by
the parties hereto, all as of the date first above written.

                                                     INVESTOR

                                                     /s/  Joseph Taylor
                                                     --------------------------
                                                     Name: Joseph Taylor


                 [Signature page to the Registration Agreement]

<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                        /s/ Douglas P. Webster
                                    --------------------------------
                                    Name: Douglas P. Webster


                 [Signature page to the Registration Agreement]


<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                              INVESTOR

                                                /s/  Terry R. Meadows
                                              ----------------------------------
                                                   Name: Terry R. Meadows

                 [Signature page to the Registration Agreement]
<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                       /s/ Louis K. Meyer
                                    -----------------------------
                                    Name: Louis K. Meyer


                 [Signature page to the Registration Agreement]

<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                        /s/ James L. Murphy
                                    -------------------------
                                    Name: James L. Murphy


                 [Signature page to the Registration Agreement]



<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                        /s/ Don S. Harvey
                                    --------------------------
                                    Name: Don S. Harvey


                 [Signature page to the Registration Agreement]



<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                      /s/ William A. Sanger
                                    ---------------------------
                                    Name: William A. Sanger


                 [Signature page to the Registration Agreement]

<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                        /s/  Dighton Packard
                                    ---------------------------
                                    Name: Dighton Packard


                 [Signature page to the Registration Agreement]

<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                      /s/ Todd Zimmerman
                                    -------------------------
                                    Name: Todd Zimmerman


                 [Signature page to the Registration Agreement]
<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                        /s/ David Mintz
                                    -------------------------
                                    Name: David Mintz


                 [Signature page to the Registration Agreement]

<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                      /s/ Steven W. Ratton, Jr.
                                    ---------------------------
                                    Name: Steven W. Ratton, Jr.


                 [Signature page to the Registration Agreement]

<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                        /s/ Randel Owen
                                    --------------------------
                                    Name: Randel Owen


                 [Signature page to the Registration Agreement]

<PAGE>

IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR

                                        /s/ Russell Harris MD
                                    -------------------------
                                    Name: Russell Harris M.D.


                 [Signature page to the Registration Agreement]

<PAGE>
IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR


                                /s/ James T. Kelly
                              --------------------
                              Name: James T. Kelly




                 [Signature page to the Registration Agreement]
<PAGE>
IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR


                               /s/ Steven B. Epstein
                             -----------------------
                             Name: Steven B. Epstein




                 [Signature page to the Registration Agreement]




                                        2
<PAGE>
IN WITNESS WHEREOF, this Registration Agreement has been duly executed by the
parties hereto, all as of the date first above written.

                                    INVESTOR


                               /s/ Michael L. Smith
                             ----------------------
                             Name: Michael L. Smith




                 [Signature page to the Registration Agreement]


                                        3


<PAGE>

                                   Schedule A

Onex American Holdings II LLC
Onex US Principals LP
EMS Executive Investco LLC
Onex EMSC Co-Invest LP
Onex Partners LP
Colby Bartlett LLC
Steven J. Shulman
Angel L. Iscovich
Jay Taylor
Terry R. Meadows
Douglas P. Webster
Louis K. Meyer
James L. Murphy
Don S. Harvey
William A. Sanger
Dighton C. Packard
Todd Zimmerman
David Mintz
Steve W. Ratton, Jr.
Randy Owen
Russell H. Harris MD
James T. Kelly
Steven B. Epstein
Michael L. Smith