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                                                                     EXHIBIT 4.3

                                                                   April 9, 2001

                          REGISTRATION RIGHTS AGREEMENT

         THIS REGISTRATION RIGHTS AGREEMENT ("Agreement") is made as of April 9,
2001, by and among Somanetics Corporation, a Michigan corporation
("Somanetics"), and the persons signing the signature page of this Agreement who
have entered into Subscription Agreements, dated April 2001, to purchase
Somanetics' common shares (the "Shareholders").

                                    RECITALS

         A.   Pursuant to Subscription Agreements, dated April 2001 (the
"Subscription Agreements"), the Shareholders have purchased Somanetics
Corporation common shares, par value $0.01 per share ("Common Shares").

         B.   To facilitate resales of Common Shares the Shareholders purchased
pursuant to the Subscription Agreements (the "Shares") and pursuant to the
requirements of the Subscription Agreements, Somanetics has agreed to provide
the Shareholders with the registration rights described in this Agreement with
respect to the Shares.

         THEREFORE, in consideration of the promises and the mutual covenants
and agreements contained in the Subscription Agreements and other good and
valuable consideration, receipt of which the parties acknowledge, the parties
agree as follows:

         1.   Definitions. For purposes of this Agreement, the following terms
shall have the following meanings:

              Person. An individual, partnership, corporation, limited liability
         company, trust or unincorporated organization, or a government or
         agency or political subdivision thereof.

              Prospectus. The prospectus included in any Registration Statement,
         as amended or supplemented by any prospectus supplement, including
         post-effective amendments and all material incorporated by reference in
         the prospectus.

              Registration Statement. Any registration statement of Somanetics
         which covers any of the Registrable Securities (as defined in Section
         2) pursuant to the provisions of this Agreement, including the
         registration statement and amendments and post-effective amendments
         thereto, the Prospectus and supplements thereto, all exhibits and all
         material incorporated by reference in the registration statement.

              SEC. The Securities and Exchange Commission.

              Securities Act. The Securities Act of 1933, as amended.

         2.   Securities Subject to this Agreement. The securities entitled to
the benefit of this Agreement (the "Registrable Securities") are all the Shares;
provided, however, that a Share shall be a Registrable Security only for so long
as the Share continues to be a Restricted Security. For




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purposes of this Agreement, each Share shall be a Restricted Security at the
date of this Agreement. A Share shall cease to be a Restricted Security when (1)
Somanetics has effectively registered the Share under the Securities Act and the
Shareholder who owns the Share, has disposed of the Share in accordance with the
Registration Statement covering the Share, (2) the Shareholder who owns the
Share, shall be eligible to sell the Share to the public pursuant to Rule 144
(or any similar provisions then in force) under the Securities Act, regardless
of whether volume or manner of sale restrictions shall apply to any such sale,
or (3) the Shareholder has otherwise transferred the Share (except as otherwise
provided in Section 7(h)).

         3.   Registration of Registrable Securities. On or before the tenth
business day after the date Somanetics issues Common Shares to any Shareholder
pursuant to a Subscription Agreement, Somanetics will use its best efforts to
cause a Registration Statement to be mailed for filing covering the number of
Registrable Securities owned by the Shareholders. Somanetics shall also use its
commercially reasonable efforts to cause such Registration Statement to become
effective within 45 days after such filing and remain effective until one year
after the last date such Common Shares are issued to such Shareholders pursuant
to the Subscription Agreements.

         4.   Registration Procedures. Somanetics shall:

              (a)  furnish to the participating Shareholders and each managing
         underwriter, if any, without charge, at least one signed copy of the
         Registration Statement and any post-effective amendment thereto,
         including financial statements and schedules, all documents
         incorporated by reference therein and all exhibits (including those
         incorporated by reference);

              (b)  deliver to the participating Shareholders and any
         underwriter, if any, without charge, as many copies of the Prospectus
         (including each preliminary prospectus) and any amendment or supplement
         thereto as they may reasonably request, but only while Somanetics is
         required to cause the Registration Statement to remain effective;

              (c)  prior to any public offering of Registrable Securities,
         register or qualify or cooperate with the participating Shareholders,
         underwriters, if any, and their respective counsel in connection with
         the registration or qualification of the Registrable Securities for
         offer and sale under the securities laws of the various states (the
         "Blue Sky Laws") and do any and all other acts or things reasonably
         necessary or advisable to effect the registration or qualification of
         the Registrable Securities covered by the Registration Statement in the
         various states; provided, however, that in no event shall Somanetics be
         obligated to qualify to do business in any jurisdiction where it is not
         now qualified or to take any action which would subject it to taxation
         or service of process in suits other than those arising out of the
         offer or sale of the securities covered by such Registration Statement
         in any jurisdictions where it is not now so subject;

              (d)  cooperate with the participating Shareholders and managing
         underwriter, if any, to prepare and deliver timely certificates
         representing Registrable Securities to be sold and not bearing any
         restrictive legends; and issue the Registrable Securities in the
         denominations and register them in the names as the managing
         underwriters, if any, may


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         request at least two (2) business days prior to any sale of Registrable
         Securities to the underwriters;

              (e)  use its best efforts to cause a Notification Form for Listing
         of Additional Shares to be filed with The Nasdaq Stock Market with
         respect to the Registrable Securities being registered or to cause
         similar required forms to be filed with the market on which similar
         securities issued by Somanetics are then listed or traded;

              (f) make available to the participating Shareholders, any
         underwriter, and any attorney or accountant retained by the
         participating Shareholders or any underwriter, for inspection all
         financial and other records, pertinent corporate documents and
         properties of Somanetics, and cause Somanetics's officers, directors
         and employees to supply all information that the participating
         Shareholders, the Shareholders' representatives, underwriters,
         attorneys or accountants may reasonably request in connection with the
         registration; provided, that such Persons shall keep confidential any
         records, information or documents that Somanetics designates as
         confidential unless a court or administrative agency requires the
         disclosure of the records, information or documents;

              Somanetics may require the participating Shareholders to furnish
         to Somanetics information regarding the participating Shareholders and
         the distribution of the Registrable Securities as Somanetics may from
         time to time reasonably request in writing.

              The Shareholders agree that, upon receipt of any notice from
         Somanetics of the happening of any of the following: (1) the SEC's
         issuance of any stop order denying or suspending the effectiveness of
         the Registration Statement or the initiation or threatening of any
         proceeding for that purpose, (2) Somanetics's receipt of any stop order
         denying registration or suspending the qualification of the Registrable
         Securities for sale or the initiation or threatening of any proceeding
         for such purpose, or (3) the happening of any event which makes any
         statement made in the Registration Statement, the Prospectus or any
         document incorporated by reference therein untrue or which requires any
         change in the Registration Statement, the Prospectus or any document
         incorporated by reference therein to make the statements not include an
         untrue statement of material fact or not omit any material fact
         required to be stated therein or necessary to make the statements
         therein not misleading in light of the circumstances then existing, the
         Shareholders shall discontinue the disposition of Registrable
         Securities until the participating Shareholders receive a supplemented
         or amended Prospectus from Somanetics or until Somanetics advises the
         participating Shareholders in writing that the participating
         Shareholders may resume the use of the Prospectus, and have received
         copies of any additional or supplemental filings which are incorporated
         by reference in the Prospectus. If Somanetics so directs, the
         Shareholders will deliver to Somanetics all copies, other than
         permanent file copies then in the Shareholders' possession, of the
         Prospectus covering the Registrable Securities at the time the
         Shareholders received the notice.

         5.   Registration Expenses. Regardless of when the Registration
Statement becomes effective, Somanetics shall bear all costs and expenses
incident to Somanetics's performance of, or compliance with, this Agreement,
including without limitation all registration and filing fees, fees



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with respect to filings required to be made with the National Association of
Securities Dealers, Inc., fees and expenses of compliance with the Blue Sky
Laws, printing expenses, messenger, telephone and delivery expenses, and fees
and disbursements of counsel for Somanetics, all independent certified public
accountants of Somanetics (including the expenses of any special audit and "cold
comfort" letters required by, or incident to, such performance), any underwriter
(excluding discounts, commissions or fees of any underwriter (the "Selling
Expenses")), selling brokers, dealer managers or similar securities industry
professionals (excluding Selling Expenses), and fees and expenses of other
Persons retained by Somanetics relating to the distribution of the Registrable
Securities (all such expenses being called "Registration Expenses"). The
participating Shareholders shall in all cases bear the Selling Expenses incident
to the registration of the participating Shareholders' Registrable Securities
and any fees of any attorney or accountant retained by any of the Shareholders.

         6.   Indemnification.


              (a)  Indemnification by Somanetics. Somanetics agrees to indemnify
         and hold harmless, to the full extent permitted by law, the
         Shareholders against all losses, claims, damages, liabilities and
         expenses, joint or several, to which the Shareholders may become
         subject under federal or state securities laws or otherwise which arise
         out of, or are caused by, Somanetics's violation of any federal or
         state securities laws, including, but not limited to, any untrue or
         alleged untrue statement of a material fact contained in any
         Registration Statement, Prospectus or preliminary prospectus or in any
         application or other request that Somanetics files, including any
         application or request filed under the Blue Sky Laws, or any omission
         or alleged omission to state therein a material fact required to be
         stated therein or necessary to make the statements therein not
         misleading, except insofar as the same are based upon an untrue or
         alleged untrue statement or omission or alleged omission so made which
         is contained in information furnished to Somanetics by any of the
         Shareholders expressly for use therein or by any Shareholder's failure
         to deliver a copy of the Registration Statement or Prospectus after
         Somanetics has furnished the participating Shareholders with a copy of
         the same. Somanetics will reimburse the Shareholders for any legal or
         other expense the Shareholders reasonably incur in connection with
         investigating or defending any such loss, claim, damage, liability,
         action or proceeding. Somanetics will also indemnify the underwriter,
         selling brokers, dealer managers and similar securities industry
         professionals participating in the distribution, their officers and
         directors and each Person who controls such persons (within the meaning
         of the Securities Act) to the same extent as provided above with
         respect to the indemnification of the Shareholders, if requested.

              (b)  Indemnification by the Shareholders. In connection with any
         Registration Statement in which any Shareholder's Registrable
         Securities are registered and sold, the participating Shareholders
         shall furnish to Somanetics the information and affidavits as
         Somanetics reasonably requests for use in connection with any
         Registration Statement or Prospectus and agree, jointly and severally,
         to indemnify and hold harmless, to the full extent permitted by law,
         Somanetics, its officers directors and each Person who controls
         Somanetics (within the meaning of the Securities Act) against any
         losses, claims, damages, liabilities and expenses resulting from any
         untrue or alleged untrue statement of a material


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         fact or any omission or alleged omission of a material fact required to
         be stated in the Registration Statement, Prospectus, preliminary
         Prospectus or any application filed under the Blue Sky Laws or
         necessary to make the statements therein not misleading, to the extent,
         but only to the extent, that the untrue statement or omission is
         contained in any information or affidavit so furnished by the
         Shareholder to Somanetics specifically for inclusion in the
         Registration Statement, Prospectus or application filed under the Blue
         Sky Laws. Somanetics shall be entitled to receive indemnities from
         underwriters, selling brokers, dealer managers and similar., securities
         industry professionals participating in the distribution, to the same
         extent as provided above with respect to information so furnished by
         the Persons specifically for inclusion in any Prospectus or
         Registration Statement.

              (c)  Conduct of Indemnification Proceedings. Any Person entitled
         to indemnification hereunder shall (1) promptly notify the indemnifying
         party of any claim with respect to which it seeks indemnification and
         (2) permit such indemnifying party to assume the defense of such claim
         with counsel reasonably satisfactory to the indemnified party. Any
         Person entitled to indemnification hereunder shall have the right to
         employ separate counsel and to participate in the defense of the claim,
         but the fees and expenses of the counsel shall be at the expense of the
         Person unless (A) the indemnifying party has agreed to pay the fees or
         expenses, (B) the indemnifying party shall have failed to assume the
         defense of the claim and employ counsel reasonably satisfactory to the
         Person, or (C) in the reasonable judgment of the Person, based upon
         advice of its counsel, a conflict of interest may exist between the
         Person and the indemnifying party with respect to the claims (in which
         case, if the Person notifies the indemnifying party in writing that the
         Person elects to employ separate counsel at the expense of the
         indemnifying party, the indemnifying party shall not have the right to
         assume the defense of the claim on behalf of the Person). The
         indemnifying party will not be subject to any liability for any
         settlement made without its consent. The indemnifying party, however,
         may not unreasonably withhold its consent. No indemnifying party will
         be required to consent to the entry of any judgment or to enter into
         any settlement which does not include as an unconditional term the
         claimant's or plaintiff's release of the indemnified party from all
         liability in respect to the claim or litigation. An indemnifying party
         who is not entitled to, or elects not to, assume the defense of a claim
         shall not be obligated to pay the fees and expenses of more than one
         counsel for all parties indemnified by the indemnifying party with
         respect to the 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 the claim, in which event the indemnifying party shall be
         obligated to pay the fees and expenses of such additional counsel or
         counsels.

              (d)  Contribution. If for any reason the indemnification provided
         for in the preceding clauses (a) and (b) is unavailable to an
         indemnified party or insufficient to hold it harmless as contemplated
         by the preceding clauses (a) and (b), then the indemnifying party shall
         contribute to the amount paid or payable by the indemnified party as a
         result of the loss, claim, damage liability or expense in the
         proportion as is appropriate to reflect (1) the relative benefits
         received by the indemnified party and the indemnifying party, (2) the
         relative fault of the indemnified party and the indemnifying party, and
         (3) any other relevant equitable considerations.


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              (e)  The indemnities provided in this Section 6 shall survive the
         Shareholders' transfer of any Registrable Securities.

         7.   Miscellaneous.

              (a)  Other Agreements. The Shareholders acknowledge that
         Somanetics has granted registration rights to others and the rights
         granted in this Agreement are subject to those rights already granted.

              (b)  Amendments and Waivers. No amendment, modification,
         supplement or waiver of any provision of this Agreement is binding on
         any party unless the party consents in writing thereto.

              (c)  Notices. Any notice or other communication required or which
         may be given under this Agreement shall be in writing and either
         delivered personally to the addressee, telegraphed, telecopied or
         telexed to the addressee, sent by overnight courier to the addressee or
         mailed, certified or registered mail, postage prepaid, and shall be
         deemed given when so delivered personally, telegraphed, telecopied or
         telexed to the addressee, or, if sent by overnight courier, on the day
         delivery is guaranteed by such courier, or, if mailed, three business
         days after the date of mailing, as follows:

                   (i)  to the Shareholders, at the most current address given
              by the Shareholders to Somanetics pursuant to the Subscription
              Agreements or otherwise.

                   (ii) To Somanetics at:

                        Somanetics Corporation
                        1653 East Maple Road
                        Troy, Michigan  48083-4208
                        Attention:  Chief Executive Officer

         Any of the foregoing may change its address for notices by notice to
the other parties.

              (d)  Governing Law and Forum. The laws of the State of Michigan
         shall govern this Agreement, its construction, and the determination of
         any rights, duties or remedies of the parties arising out of, or
         relating to, this Agreement (regardless of the laws that might
         otherwise govern under applicable Michigan principles of conflicts of
         law). The parties acknowledge that the United States District Court for
         the Eastern District of Michigan or the Michigan Circuit Court for the
         County of Oakland shall have exclusive jurisdiction over any case or
         controversy arising out of, or relating to, this Agreement and that all
         litigation arising out of, or relating to, this Agreement shall be
         commenced in the United States District Court for the Eastern District
         of Michigan or in the Oakland County (Michigan) Circuit Court. Each of
         the parties consents to be subject to personal jurisdiction of the
         courts of Michigan, including the federal courts in Michigan.


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              (e)  Counterparts. This Agreement may be executed in two or more
         counterparts, each of which shall be deemed an original, but all of
         which together shall constitute one and the same instrument.

              (f)  Interpretation. The Section headings contained in this
         Agreement are for the purposes of reference, are not part of the
         agreement of the parties and shall not in any way affect the meaning or
         interpretation of this Agreement.

              (g)  Severability. If any provision of this Agreement is
         determined to be illegal or invalid, such illegality or invalidity
         shall have no effect on the other provisions of this Agreement, and all
         other provisions of this Agreement shall remain valid, operative and
         enforceable.

              (h)  Assignment. The rights granted to the Shareholders pursuant
         to this Agreement shall not be assignable without the written consent
         of Somanetics.

         IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first written above.

                               SOMANETICS CORPORATION

                               By:  /s/ Bruce J. Barrett
                                    --------------------------------------------


                                        Its:  President and CEO
                                              ----------------------------------



/s/ Silas R. Anthony Jr.
-------------------------------


Pequod Investments LP
-------------------------------
/s/ Jonathan Gallen
-------------------------------
Its:  General Partner
-------------------------------


Pequod International, Ltd.
-------------------------------
/s/ Jonathan Gallen
-------------------------------
Its:  Director


/s/ John S. Lemak
-------------------------------


AJ Investors
-------------------------------
/s/ Adam Katz
-------------------------------
Its:  General Partner
-------------------------------


/s/ Robert R. Henry
-------------------------------


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/s/ Michael A. Nicolais
-------------------------------


PNG Enterprise Foundation
-------------------------------
/s/ Paul Geyer
-------------------------------
Its:  Principal
-------------------------------


Geyer Engineering Ltd.
-------------------------------
/s/ Paul Geyer
-------------------------------
Its:  President
-------------------------------


/s/ Norman C. Fields
-------------------------------


/s/ Robin Fields
-------------------------------


/s/ Suzan Ehrman
-------------------------------


/s/ Harrison H. Augur
-------------------------------


/s/ Barry Fingerhut
-------------------------------


Tradewind Fund I LP
-------------------------------
/s/ Elliot Sloyer
-------------------------------
Its: Managing Director
-------------------------------


/s/ Elliot Sloyer
-------------------------------


/s/ Joseph P. von Meister
-------------------------------


Trust U/A Dtd. 12/23/76
-------------------------------
/s/ John P. de Neufville
-------------------------------
Its:  Trustee
-------------------------------


DN&C Capital
-------------------------------
/s/ John P. de Neufville
-------------------------------
Its:  General Partner
-------------------------------


Talmor Capital Management, LLC
-------------------------------
/s/ Edmund H. Melhado
-------------------------------
Its:  President
-------------------------------

Brean Murray & Co., Inc. Profit Sharing Trust
---------------------------------------------
/s/ A. Brean Murray
-------------------------------
Its:  Chairman, CEO, and President
----------------------------------



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