Document:

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                                                                   Exhibit 10.25

                        EIGHTH AMENDMENT TO OFFICE LEASE
                        --------------------------------

      THIS EIGHTH AMENDMENT TO OFFICE LEASE (this "Eighth Amendment") is made as
of the later of the dates accompanying a signature by Landlord and Tenant below,
by and between BERKELEY FIRST CITY, LTD., a Delaware limited partnership
("Landlord"), and PENSON WORLDWIDE, INC., a Delaware corporation ("Tenant").

                                   WITNESSETH:
                                   -----------

      WHEREAS, Landlord's predecessor-in-interest, F/P/D Master Lease, Inc., a
Texas corporation ("Original Landlord"), and Tenant's predecessor-in-interest,
Service Asset Management Company, a North Carolina corporation ("Original
Tenant"), entered into that certain Office Lease dated as of May 20, 1998 (the
"Original Lease"), with respect to the lease of approximately 31,478 square feet
of Net Rentable Area (as defined in the Lease) on the 14th floor known as Suite
1400 of that certain office building known as 1700 Pacific (the "Building"),
which Original Lease was amended by (i) that certain First Amendment to Office
Lease dated as of July 16, 1998, (ii) that certain Second Amendment to Office
Lease dated as of February 17, 1999, (iii) that certain Third Amendment to
Office Lease dated as of September 20, 1999, (iv) that certain Fourth Amendment
to Office Lease dated as of November 30, 1999, (v) that certain Fifth Amendment
to Office Lease dated as of May 25, 2000, (vi) that certain Sixth Amendment to
Office Lease dated as of January 9, 2001, and (vi) that certain Seventh
Amendment to Office Lease dated as of July 9, 2001 (the Original Lease, as so
amended, being hereinafter sometimes called the "Current Lease"), which
currently relates to approximately 68,524 square feet of Net Rentable Area (as
that term is defined in the Lease) on the 14th, 15th and 20th floors of the
Building (such approximately 68,524 square feet of Net Rentable Area being
hereinafter sometimes called the "Current Premises");

      WHEREAS, as documents ancillary to the Current Lease, Original Landlord
and Original Tenant also entered into that certain Temporary Space License
Agreement dated as of November 8, 1999 (the "Garage Space License"), which
granted Original Tenant a temporary license to use space on the third floor of
the On-Site Garage (as that term is defined in the Original Lease) for a back-up
electrical generator, and that certain Antenna Site License Agreement dated as
of February 15, 2001 (the "Antenna License"), which granted Original Tenant a
license to use space on the roof of the Building for specified "Site Equipment"
(as that term is defined in the Antenna License);

      WHEREAS, Original Landlord sold the Building to Landlord in June 2005;
therefore, Landlord is the current owner of the Building;

      WHEREAS, in September 2000, Original Tenant changed its name to Penson
Financial Services, Inc., as confirmed by an Application for Amended Certificate
of Authority filed by Original Tenant with the Secretary of State of the State
of Texas on September 25, 2000;

      WHEREAS, prior to the date of this Eighth Amendment, Original Tenant has
assigned all of its rights and obligations under the Current Lease, the Garage
Space License and the

EIGHTH AMENDMENT TO OFFICE LEASE

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Antenna License to Tenant, which is the ultimate parent company of Original
Tenant; and Tenant has assumed all such rights and obligations; and

      WHEREAS, Landlord and Tenant now desire to amend the Current Lease to
expand the Current Premises, to extend the Term of the Current Lease (and,
accordingly, the terms of the Garage Space License and the Antenna License) and
to modify certain other provisions of the Current Lease as set forth herein,
with the Current Lease, as modified by this Eighth Amendment, being sometimes
referred to herein as "this Lease".

      NOW, THEREFORE, for and in consideration of the mutual covenants contained
in this Eighth Amendment, and other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, Landlord and Tenant do hereby
agree as follows:

      1.    Expansions of Current Premises.
            ------------------------------

      (a) Effective as of July 1, 2006 (the "2006 Expansion Effective Date"),
the Original Lease is hereby amended to include within the Leased Premises
approximately 13,084 Rentable Square Feet on the 19th floor of the Building, as
shown more particularly on Exhibit "A" attached hereto (such approximately
13,084 Rentable Square Feet being hereinafter sometimes called the "2006
Expansion Premises"); and as of the 2006 Expansion Effective Date, the 2006
Expansion Premises shall be added to the definition of "Leased Premises" as that
term is used in this Lease. Accordingly, as of the 2006 Expansion Effective Date
the Leased Premises for Tenant shall consist of approximately 81,608 Rentable
Square Feet on the 14th, 15th, 19th and 20th floors of the Building.

      (b) Effective as of February 1, 2008 (the "2008 Expansion Effective
Date"), this Lease is hereby amended to include within the Leased Premises the
approximately 13,084 remaining Rentable Square Feet on the 19th floor of the
Building, as shown more particularly on Exhibit "A" attached hereto (such
approximately 13,084 remaining Rentable Square Feet being hereinafter sometimes
called the "2008 Expansion Premises"); and as of the 2008 Expansion Effective
Date, the 2008 Expansion Premises shall be added to the definition of "Leased
Premises" as that term is used in this Lease. Accordingly, as of the 2008
Expansion Effective Date the Leased Premises for Tenant shall consist of
approximately 94,692 Rentable Square Feet on the 14th, 15th, 19th and 20th
floors of the Building.

      (c) The square footage recitations in this Paragraph 1 are subject to
Tenant's further rights to expand pursuant to its right of first refusal
prescribed in Paragraph 8 below.

      2. Extension of the Term of This Lease. The Term of the Current Lease, as
well as the terms of the Garage License Agreement and the Antenna License
Agreement, are scheduled to expire after the close of business on December 31,
2008. By their execution of this Eighth Amendment, Landlord and Tenant hereby
agree that the Term of this Lease for the Current Premises, the 2006 Expansion
Premises and the 2008 Expansion Premises shall continue through and including
June 30, 2016 (with the date of June 30, 2016 being hereby substituted for the
date of November 30, 2008 in the definition of "Expiration Date" on Page 2 of
the Original Lease). Similarly, the terms of the Garage License Agreement and
the Antenna License Agreement shall

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be extended accordingly. This Paragraph 2, however, is subject to the provisions
of Paragraph 11 below.

      3. Minimum Rent. The definition of Minimum Rent on Page 2 of the Original
Lease is hereby amended to be as follows: (a) for the period of the Lease Term
through and including June 30, 2006, such Minimum Rent shall be as stated in the
Current Lease; (b) commencing on the 2006 Expansion Effective Date and
continuing through and including January 31, 2008, such Minimum Rent shall be
$115,611.33 per month; and (c) commencing on the 2008 Expansion Effective Date
and continuing through and including the Expiration Date of this Lease, such
Minimum Rent shall be $134,147.00 per month.

      4.    Tenant's Proportionate Share; Base Year for Operating Costs.
            -----------------------------------------------------------

      (a) For the period of the Lease Term through and including June 30, 2006,
Tenant's Proportionate Share of any Excess Operating Costs shall continue to be
calculated as prescribed in the Current Lease. Commencing on the 2006 Expansion
Effective Date and continuing through and including January 31, 2008, Tenant's
Proportionate Share of any Excess Operating Costs shall be 6.088%, i.e., based
upon a total of 81,608 Rentable Square Feet Rental Square in the Leased
Premises, in lieu of the 5.112% share set forth in Paragraph 4 of the
above-mentioned Sixth Amendment to Office Lease. Commencing on the 2008
Expansion Effective Date and continuing through and including the Expiration
Date of this Lease, Tenant's Proportionate Share of any Excess Operating Costs
shall be 7.064%, i.e., based upon the total of 94,692 Rentable Square Feet
Rental Square in the Leased Premises.

      (b) On and after the 2006 Expansion Effective Date and continuing through
and including the Expiration Date of this Lease the Base Year for Operating
Costs shall become calendar year 2006.

      5.    "AS IS"; Improvement Allowances.
            -------------------------------

      (a) Tenant acknowledges that it has made a complete examination and
inspection of the Premises and accepts the same in its current condition, "AS
IS, WHERE IS", without recourse to Landlord, and Landlord shall have no
obligation to complete any improvements to the Premises. ADDITIONALLY, LANDLORD
MAKES NO WARRANTIES, EXPRESS OR IMPLIED, WITH RESPECT TO THE LEASEHOLD
IMPROVEMENTS IN THE PREMISES. ALL IMPLIED WARRANTIES WITH RESPECT THERETO,
INCLUDING BUT NOT LIMITED TO THOSE OF MERCHANTABILITY, HABITABILITY AND FITNESS
FOR A PARTICULAR PURPOSE, ARE EXPRESSLY DISCLAIMED, NEGATED AND WAIVED. This
Paragraph 5(a), however, is subject to the lease amendments set out in Paragraph
12 below.

      (b) The parties further agree that at any time prior to October 1, 2006,
Tenant may request from Landlord a reimbursement for out-of-pocket costs which
Tenant has incurred in remodeling the Current Premises and/or the 2006 Expansion
Premises; and provided that Tenant is not then in default under this Lease
beyond applicable grace periods, Landlord will reimburse Tenant for up to
$735,140.00 of Tenant's out-of-pocket costs. Such $735,140.00 amount has been
calculated by multiplying $30.00 times the Rentable Square Feet in the 2006
Expansion

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Premises and $5.00 times the Rentable Square Feet in the Current Premises;
however, the entire $735,140.00 (the "2006 Allowance") may be used for
improvements in the Current Premises, in the 2006 Expansion Premises, or
allocated between the Current Premises and the 2006 Expansion Premises as Tenant
so chooses. Notwithstanding the immediately preceding sentence to the contrary,
the 2006 Allowance shall be reduced by 5% of the amounts so requested by Tenant,
in order to account for a construction management fee payable to Landlord on
account of Landlord's coordination efforts and costs in facilitating Tenant's
remodeling activities. In connection with the remodeling for which a
reimbursement is prescribed in this subparagraph (b), Landlord and Tenant
further agree that the construction contract for such remodeling shall be
executed by Landlord after approval thereof by both Landlord and Tenant;
moreover, both Landlord and Tenant also agree that Landlord shall pay the cost
of such remodeling until the above-stated allowance has been reduced to zero,
after which time Tenant shall pay all remaining costs and shall indemnify
Landlord from any claims by the contractors on account of such remaining costs.

      (c) The parties further agree that at any time which is after the 2008
Expansion Effective Date and prior to May 1, 2008, Tenant may request from
Landlord a reimbursement for out-of-pocket costs which Tenant has incurred in
remodeling the 2008 Expansion Premises; and provided that Tenant is not then in
default under this Lease beyond applicable grace periods, Landlord will
reimburse Tenant for up to $330,371.00 (the "2008 Allowance") of Tenant's
out-of-pocket costs in remodeling the 2008 Expansion Premises, such $330,371.00
amount for the 2008 Allowance having been calculated by multiplying $30.00 times
the Rentable Square Feet in the 2008 Expansion Premises and then multiplying
that product times 84.1667% (the percentage of the 120-month Lease Term
prescribed in Paragraph 2 above which will be remaining as of the 2008 Expansion
Effective Date). Notwithstanding the immediately preceding sentence to the
contrary, the 2008 Allowance shall be reduced by 5% of the amounts so requested
by Tenant, in order to account for a construction management fee payable to
Landlord on account of Landlord's coordination efforts and costs in facilitating
Tenant's remodeling activities.

      6.    Parking.
            -------

      (a) For the period of the Lease Term through and including June 30, 2006,
Tenant's parking privileges shall continue to be as prescribed in the Current
Lease. Effective as of the 2006 Expansion Effective Date and continuing through
January 31, 2008, Tenant's parking permits, as originally explained in
Paragraph53 of the Original Lease, shall be amended to provide that Landlord
shall provide Tenant, in lieu of the parking permits specified in the Current
Lease, sixteen (16) permits for unassigned, unreserved parking in the On-Site
Garage, as that term is defined in the Current Lease (the "On-Site Unreserved
Permits") and ninety (90) permits for unassigned, unreserved parking in the
Off-Site Garage, as that term is defined in the Current Lease (the "Off-Site
Permits").

      (b) Effective as of the 2008 Expansion Effective Date and continuing
throughout the remainder of the Term of this Lease, Tenant's parking permits, as
originally explained in Paragraph53 of the Original Lease, shall be amended to
provide that Landlord shall provide Tenant, in lieu of the parking permits
specified in subsection (a) immediately above, eighteen (18) permits for
unassigned, unreserved parking in the On-Site Garage, as that term is defined in

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the Current Lease (the "On-Site Unreserved Permits") and one hundred two (102)
permits for unassigned, unreserved parking in the Off-Site Garage, as that term
is defined in the Current Lease (the "Off-Site Permits").

      (c) For the period of the Lease Term through and including June 30, 2006,
Tenant's Parking Fees shall continue to be calculated as prescribed in the
Current Lease. Effective as of the 2006 Expansion Effective Date and throughout
the remainder of the Term of this Lease, Tenant shall pay Landlord or Landlord's
designated agent, as monthly Parking Fees, the sum of the following: (i) an
amount determined by multiplying (A) $200.00, plus applicable sales tax, per
month, times (B) the number of On-Site Unreserved Permits which Tenant then has
a right to under this Eighth Amendment; plus (II) an amount determined by
multiplying (A) $100.00 per month, plus applicable sales tax, times (B) the
number of Off-Site Permits, which Tenant then has a right to under this Eighth
Amendment, Such Parking Fees shall be payable in accordance with the Parking
Agreement.

      (d) In addition to the parking permits prescribed above, Tenant may
request one or more additional permits for unreserved parking in either the
Off-Site Garage or the On-Site Garage (the "Availability Permit(s)"); and
Landlord agrees that for as long as Landlord in its sole discretion deems it
able to do so, Landlord shall make available one or more of the Availability
Permit(s) requested by Tenant. All Availability Permits which Tenant may acquire
shall be issued solely on a month-to-month basis and subject to recall, in whole
or in part, based on the then present and anticipated future parking needs for
the Building, as determined by Landlord in its sole discretion. The Parking Fees
for any Availability Permit(s) which Tenant may acquire shall be the same as
prescribed in the immediately preceding grammatical paragraph; however, Landlord
at its option may revise the Parking Fees for Availability Permit(s) to the
Parking Fees charged from time to time by Landlord to other users of such
parking permits. Notwithstanding the foregoing, each Availability Permit will be
leased solely on a month-to-month basis, and either Landlord or Tenant may
terminate the lease of an Availability Permit by providing the other written
notice of its election to terminate the lease of such Availability Permit no
less than thirty (30) days prior to any such termination.

      7. Tenant's Monument Sign. Landlord and Tenant acknowledge that the
Building does not currently have an exterior, ground level, tenant monument
sign. Landlord agrees to cooperate in good faith with Tenant to determine a
mutually acceptable location either for a monument sign or for ground floor
signage on the Building, as well as the size, shape and general concept scheme
of the sign. The monument sign, if erected, would be designed and installed at
Landlord's cost. During the Term of this Lease, Tenant, at Tenant's cost, would
have the right to one line of identification on the monument sign or ground
floor signage on the Building.

      8. Tenant's Right of First Refusal. Paragraph 60 of the Original Lease, as
well as Paragraph 8 of the above-described Fourth Amendment to Office Lease and
the above-described Fifth Amendment to Office Lease, are hereby rendered
inoperative and of no further force or effect. Instead, Landlord hereby agrees
that throughout the Term of this Lease and as long as no uncured event of
default has occurred under this Lease, Tenant shall have a right of first
refusal to lease any vacant space in the area(s) located on the 14th floor
though and including the 21st

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floor and in the area(s) located on the 24th floor through and including the
26th floor (i.e., all of the so-called Low-Mid Rise Elevator Stack of the
Building other than the 22nd and 23rd floors), as well as any vacant space
contiguous to the Premises in the so-called Low Rise Elevator Stack of the
Building (with all such the designated areas being hereinafter referred to as
the "Designated Areas"), which Landlord intends to market for lease to a party
or parties other than the current tenant(s) thereof. The right granted by this
Paragraph 8 shall apply throughout the Term of this Lease and any renewals or
extensions thereof; however, such right is subject to the following terms and
conditions:

    If a proposed tenant, i.e., other than the current tenant in the space,
    gives Landlord an expression of interest in leasing then vacant space within
    any of the Designated Areas (either as a separate leased premises or
    together with space outside the Designated Areas), and if Landlord intends
    to enter into a lease with the proposed tenant for such space, Landlord
    shall deliver to Tenant a written notice which (i) specifies the portion or
    portions of the Designated Areas and, if applicable, any other space in the
    Building which the proposed tenant wishes to lease and Landlord intends to
    allow to be leased along with the portion or portions of the Designated
    Areas (all such space being referred to collectively as the "Refusal
    Space"), (ii) identifies the proposed tenant, (iii) summarizes what Landlord
    considers to be the most significant business terms of the proposed lease,
    and (iv) offers to lease the Refusal Space to Tenant on the same terms and
    conditions as Landlord intends to offer to the proposed tenant. Tenant shall
    then have a period of three (3) business days from the delivery of such
    notice (the "Delivery Date") to accept the lease offered by Landlord. If
    within such 3 business day period Tenant does not give Landlord written
    notice of its acceptance of the lease offered by Landlord (time being of the
    essence), then Landlord shall be entitled to execute with the proposed
    tenant identified in Landlord's notice to Tenant (or with an "affiliated
    entity," i.e., an entity affiliated to such identified proposed tenant by
    common ownership), a lease of the Refusal Space for the same or better (for
    Landlord) terms as stated in the notice to Tenant. If within one hundred
    eighty (180) days after the Delivery Date Landlord does so execute a lease
    of the Refusal Space, this right of first refusal shall abate as to that
    portion of the Refusal Space which is in the Designated Areas, until the
    expiration of such lease and any extensions or renewals thereof. If Landlord
    does not execute a lease of the Refusal Space with the proposed tenant or an
    affiliated entity within one hundred eighty (180) days after the Delivery
    Date, then Landlord shall again comply with the terms of this Paragraph 8 in
    marketing the portion of the Refusal Space which is in the Designated Areas.

      9. Tenant's Conditional Right to Create a Separate Lease for the 20th
Floor. Tenant advises Landlord that it has formed or is in the process of
forming a new entity to be named SAMCO Holdings, Inc. ("SAMCO Holdings"), as
described in Tenant's Form S-1 filed with the United States Securities and
Exchange Commission on September 15, 2005, and specifically in the paragraphs
entitled "Split off transaction" which are included in the section of that Form
S-1 which is entitled "Management's discussion and analysis of financial
condition and results of operations". Landlord hereby agrees that as long as no
uncured event of default has occurred under this Lease, then at any time after
the 2006 Expansion Effective Date, Tenant may request Landlord to remove the
20th floor portion of the Premises (the "20th Floor Premises") from the

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Premises covered by this Lease in exchange for Landlord's lease of the 20th
Floor Premises with SAMCO Holdings (the "SAMCO Lease"); and Landlord agrees that
it will accommodate Tenant's request if in Landlord's judgment, not to be
unreasonably withheld, the financial condition and business operations of SAMCO
Holdings are sufficient to assure Landlord of SAMCO Holdings's likely compliance
with the terms of the SAMCO Lease. If such removal of the 20th Floor Premises
and such SAMCO Lease is effected, then (i) the terms of the SAMCO Lease will be
exactly the same as the terms of this Lease, with the exception that all terms
relating to Rentable Square Footage, either directly or indirectly (such as
rentals, parking permits, etc.) shall be reduced proportionately relative to the
Rentable Square Feet in the 20th Floor Premises, (ii) the terms of this Lease
relating to Rentable Square Footage, either directly or indirectly, will be
revised to specify terms which are proportionately reduced from what existed
immediately prior to the SAMCO Lease, and (iii) Tenant shall have no further
obligation under this Lease with respect to the 20th Floor Premises.

      10.   Tenant's Renewal Option.  Landlord and Tenant hereby agree that
Paragraph 61 of the Original Lease (entitled "Option to Extend Lease Term")
shall continue to apply to this Lease. i.e., there is one remaining 5-year
renewal option available to Tenant pursuant to such Paragraph 61.

      11. Tenant's Termination Right. Notwithstanding anything contained in this
Lease to the contrary, Landlord agrees that as long as no uncured event of
default has occurred and remains uncured under this Lease, Tenant may terminate
this Lease (and, accordingly, the Garage License Agreement and the Antenna
License Agreement) effective as of the close of business on the last day of any
calendar month (the "Termination Month") after December 31, 2013, which is at
least twelve (12) full months subsequent to the month (the "Notice Month")
during which a written termination notice (the "Termination Notice") is
delivered by Tenant to Landlord, it being agreed by Landlord and Tenant that
such written Termination Notice may be delivered at any time after -- but not
before -- December 31, 2012. Tenant agrees that if it delivers to Landlord a
Termination Notice as contemplated in this Paragraph 11, then it shall be
unconditionally and irrevocably obligated as follows:

      (a)   Paragraph 2 hereinabove shall be deemed amended to provide that the
            Term of this Lease (and, accordingly, the terms of the Garage
            License Agreement and the Antenna License Agreement) ends on the
            last date of the Termination Month.

      (b)   Tenant must remain current in its rentals and other obligations
            under this Lease through the date of termination.

      (c)   Tenant's Termination Notice must be accompanied by Tenant's payment
            to Landlord (i.e., a payment in addition to all rentals and other
            financial obligations specified elsewhere in this Lease) of a
            Termination Fee in the amount described below.

      (d)   Tenant must vacate the Premises by the close of business on the
            last day of the Termination Month.

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For purposes of this Paragraph 11, the term "Termination Fee" shall equal the
following:

      (i)   Unless the Premises has increased due to Tenant's exercise of a
            right of first refusal as prescribed in Paragraph 8 above, the
            Termination Fee will be $1,631,102.50.

      (ii)  If the Premises has increased due to Tenant's exercise of a right of
            first refusal as prescribed in Paragraph 8 above, or if for any
            other reason the Premises has been expanded to a size greater than
            as is provided in this Eighth Amendment, the Termination Fee will be
            equal to the sum of $1,631,102.50 plus 50% of the remaining lease
            obligation for the additional space leased.

      12. Further Revisions to the Current Lease. Effective immediately, the
notice address for Landlord is as follows: Management Office, Suite L 100, 1700
Pacific Avenue, Dallas, Texas 75201, or at such other place as Landlord may
designate from time to time in writing. In addition, Landlord hereby agrees to
the following additional revisions to the Current Lease:

      (a)   The next-to-last sentence in the first subparagraph in Paragraph
            7 of the Original Lease (with the subparagraphs in Paragraph 7 of
            the Original Lease being indented with "bullet" paragraph
            identifications) states:  "Tenant shall pay Landlord as
            additional Rent for extra service within 5 days after receipt of
            a bill therefor the greater of (A) the actual cost of the extra
            service [if more than one tenant has requested and is furnished
            after-hours HVAC service for the same hour(s) the charge will be
            prorated if reasonably possible], or (B) $50 per hour per floor
            (whole or partial) of after-hours HVAC service."  Landlord and
            Tenant hereby agree that effective as of the 2006 Expansion
            Effective Date, that sentence shall be deleted in its entirety
            from the Lease and the following sentence substituted in its
            place:  "Tenant shall reimburse Landlord as additional Rent for
            after-hours HVAC service the actual cost incurred by Landlord,
            without markup, in furnishing the after-hours HVAC service to
            Tenant, such reimbursement to be paid by Tenant to Landlord
            within five (5) business days after Tenant's receipt of a written
            statement from Landlord."

      (b)   Supplementing the requirements imposed upon Landlord pursuant to
            the first sentence in Paragraph 7 of the Original Lease, Landlord
            agrees that it shall ensure that the Building common areas
            (including restrooms) on any floor which Tenant is an occupant
            are in compliance with all Applicable Laws (as defined in
            Paragraph 14(a) of the Original Lease), including but not limited
            to the Americans with Disabilities Act (ADA) and Texas
            Accessibility Standards (TAS), both at the time of Tenant's
            possession of the Premises and throughout the extended Term of
            this Lease as prescribed in Paragraph 2 above, as well as any
            extensions thereof.  In this regard, Landlord further assures
            Tenant that such common areas are currently in compliance with
            Applicable Laws.

      (c)   Also supplementing the requirements imposed upon Landlord
            pursuant to the first sentence in Paragraph 7 of the Original
            Lease, Landlord agrees that to the extent

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            mold is found in the Project which is reasonably deemed likely to
            cause any health concerns to people who work in, or visit, the
            Project, and to the extent that the mold was not created by Tenant,
            then Landlord shall cause such mold to be removed from the Project
            as soon as is reasonably possible so as not to cause any health
            concerns to people who work in, or visit, the Project.

      (d)   Supplementing the requirements imposed upon Landlord pursuant to
            the first sentence in Paragraph 38(e) of the Original Lease,
            Landlord agrees that it shall comply with all laws applicable to
            hazardous substances (as that term in defined in Paragraph 38(a)
            of the Original Lease.  Landlord agrees that Tenant shall have no
            obligations as to hazardous substances that exist in the Project
            as of the date this Eighth Amendment is signed or that
            subsequently are found in the Project, except to the extent such
            hazardous substances are placed in the Project by Tenant.

      (e)   The following sentence is hereby added to the conclusion of
            Paragraph 9(a) of the Original Lease: "Notwithstanding anything to
            the contrary in this Paragraph 9(a), Landlord shall not be permitted
            to collect more than 100% of the Operating Costs from tenants in the
            Project."

      (f)   Paragraph 57 of the Original Lease is hereby deleted in its
            entirety.

      (g)   Paragraph 27(h) is hereby deleted in its entirety. Landlord agrees
            that Tenant's abandonment of the Premises will not be a violation of
            this Lease as long as Tenant is not in default either as to its
            payment obligations under this Lease or as to Tenant's other
            obligations prescribed in this Lease that are not related to its
            occupancy of the Premises (such as maintaining insurance as
            prescribed in this Lease).

      (h)   Supplementing Paragraph 32(a) of the Original Lease, Landlord hereby
            assures Tenant that other than the ground leases reflected in
            Exhibit B of the Original Lease, there are no other leases affecting
            the Premises. Landlord further assures Tenant that the assurance of
            quiet enjoyment which is contained in Paragraph 33 of the Original
            Lease is in no way reduced or adversely affected by Landlord's
            disclosure of such ground leases to Tenant.

      (i)   Supplementing subparagraph (i) of Paragraph 11(a) of the Original
            Lease, Landlord hereby agrees that all of the subsidiaries and
            "Affiliates" (defined in such subparagraph in the Original Lease)
            shall be entitled to occupy and use the Premises during the Term of
            this Lease.

      13. Brokerage Commissions. Landlord and Tenant hereby represent and
warrant to each other that, other than commissions due and payable by Landlord
to Trammell Crow Company (representing Landlord in this transaction) and The
Staubach Company - Southwest, Inc. (representing Tenant in this transaction),
each of whom will be compensated by Landlord pursuant to a separate commission
agreement between the Landlord and each respective

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brokerage company so named, no commission is due and payable to any broker or
other leasing agent in connection with this Eighth Amendment as a result of its
own dealings with any broker or leasing agent. In this regard, Landlord and
Tenant hereby agree to indemnify and hold each other harmless from and against
all loss, damage, cost and expense (including reasonable attorneys' fees)
suffered by the other party as a result of a breach of the foregoing
representation and warranty.

      14. SNDA. Contemporaneously with the execution of this Eighth Amendment,
Landlord has delivered to Tenant a Subordination, Non-Disturbance and Attornment
Agreement ("SNDA") from Landlord's mortgagee, on the standard form used by such
mortgagee which either (i) has been executed by Landlord's mortgagee or (ii) has
been accompanied by evidence acceptable to Tenant that the mortgagee will
execute such SNDA promptly after Tenant executes it.

      15. Full Force and Effect. In the event any of the terms of the Current
Lease conflict with the terms of this Eighth Amendment, the terms of this Eighth
Amendment shall control. Except as amended hereby, all terms and conditions of
the Current Lease, as well as the terms of the Garage Space License and the
Antenna License, shall remain in full force and effect, and Landlord and Tenant
hereby ratify and confirm the Lease as amended hereby. The Current Lease, as
amended herein, together with the Garage Space License and the Antenna License,
constitute the entire agreement between the parties hereto, and no further
modification of this Lease shall be binding unless evidenced by an agreement in
writing signed by Landlord and Tenant.

      16. Execution Requirement; Effective Date; Counterparts; Telecopy. The
submission by Landlord of this Eighth Amendment to Tenant for examination,
negotiation or signature does not constitute an option for, or a representation
by, Landlord. This Eighth Amendment shall be effective if and when (and only if
and when) it has been executed by both Landlord and Tenant. When such condition
has been satisfied, the effective date of this Eighth Amendment shall be the
latest date accompanying a signature by Landlord and Tenant below; and if either
or both signatures fail to be accompanied by a date, then the date of such
signature(s) shall be established by the best alternative evidence. Counterpart
execution and delivery of a signed copy by telecopy transmission shall be
effective with regard to the signing party(ies).

                                       10

EIGHTH AMENDMENT TO OFFICE LEASE

<PAGE>

LANDLORD:

BERKELEY FIRST CITY, L.P.,
a Delaware limited partnership

By:   KAL First City L.L.C., a Delaware
      limited liability company and sole
      general partner

      By:/s/ Jon Hamilton
         ---------------------------
            Jon Hamilton, Manager

Date: April 12, 2006

TENANT:

PENSON WORLDWIDE, INC.,
a Delaware corporation

By:/s/ Roger J. Engemoen, Jr.
   ---------------------------------------------------------
Name: Roger J. Engemoen, Jr.
     -------------------------------------------------
Title:      Chairman
      ------------------------------------------

Date: April 12, 2006

                                       11

EIGHTH AMENDMENT TO OFFICE LEASE<PAGE>
                                                                   EXHIBIT 10.27

(GUARANTY BANK LOGO)

                                  May 8, 2006

Penson Worldwide, Inc.
SAMCO Holdings Inc.
SAI Holdings, Inc.
1700 Pacific Avenue Suite 1400
Dallas, Texas 75201

Attention: Roger Engemoen

           Re: Reorganization of SAMCO Division
               --------------------------------

Dear Rocky:

           We refer to that certain Amended and Restated Loan Agreement dated as
of April 30, 2001 (as has been amended, restated, modified or supplemented from
time to time, the "Loan Agreement") between Guaranty Bank ("Bank") and SAI
Holdings, Inc., a Texas corporation, formerly known as Service Asset
Investments, Inc. ("Borrower") pursuant to which Bank extended credit and made
certain advances to Borrower as described therein. Capitalized terms used herein
and not otherwise defined shall have the meanings given to such terms as in the
Loan Agreement. As security for the Obligations, (i) Borrower executed that
certain Fifth Amended and Restated Stock Pledge Agreement dated as of October 4,
2004 the "Borrower Pledge Agreement") pledging that certain collateral described
therein and (ii) Penson Worldwide, Inc., a Delaware corporation ("PWI"),
executed that certain Amended and Restated Penson Worldwide Stock Pledge
Agreement dated as of October 4, 2004 (the "Penson Worldwide Pledge Agreement,"
together with the Borrower Pledge Agreement, the "Pledge Agreements").

           You have informed us that pursuant to a Reorganization Agreement
("Reorganization Agreement") to be entered between PWI, SAMCO Holdings, Inc.
("SHI"), Penson Financial Services, Inc. ("PFSI"), SAMCO Capital Markets Inc.
("SCMI") and Borrower, certain assets, comprising the SAMCO Division of the
Penson group, are to be transferred to SHI. These assets include the shares of
SAMCO Financial Advisors Inc. ("SFAI"), SAMCO Financial Services, Inc. ("SFSI")
and SAMCO BD LLC ("SBD") which are currently pledged pursuant to the Pledge
Agreements in favor of Bank as security for the Obligations. In addition, PFSI's
SAMCO Capital Markets division shall be transferred to SCMI.

           You have also informed us that Penson Worldwide, Inc. is making its
first public offering of its common stock, par value $0.01 per share (the "IPO")
and with the proceeds will be paying off the Obligations in full and terminating
the Loan Agreement (the "Payoff").

           Borrower acknowledges and agrees by its execution below that (i) this
letter is a Loan Document for all purposes and (ii) if the IPO and the Payoff
fails to occur within thirty days of the date hereof, it shall constitute an
Event of Default under the Loan Agreement.

<PAGE>
           This letter confirms (i) our consent to the reorganization of the
SAMCO Division and the transfer to SAMCO Holdings, Inc. of the shares of SFSI,
SFAI, and SBD (collectively the "SAMCO Securities"), (ii) our consent to the
transfer of PSFI's SAMCO Capital Markets division to SCMI, and (iii) our
agreement that upon the consummation of the reorganization pursuant to the
Reorganization Agreement on terms and conditions satisfactory to the Bank (the
"Reorganization") the security interests granted in favor of Bank in respect of
the SAMCO Securities shall be released, provided, however, that the Pledge
Agreements shall remain in full force and effect and all Collateral described
therein, other than the SAMCO Securities, shall remain pledged as security for
the Obligations. We agree, upon your request following consummation of the
Reorganization, to file termination statements releasing Bank's security
interest in the SAMCO Securities, to return all stock certificates and stock
powers representing the SAMCO Securities, and to take such other actions as are
necessary, to terminate our security interest in the SAMCO Securities.

                                             Very truly yours,

                                             GUARANTY BANK

                                             By: /s/ Caswell O. Robinson, Jr.
                                                 -------------------------------
                                                 Name: Caswell O. Robinson, Jr.
                                                 Title: Senior Vice President

ACKNOWLEDGED AND AGREED:

PENSON WORLDWIDE, INC.

By: /s/ Roger J. Engemoen, Jr.
    --------------------------
    Name: Roger J. Engemoen, Jr.
    Title: Chairman

SAI HOLDINGS. INC.

By: /s/ Roger J. Engemoen, Jr.
    --------------------------
    Name: Roger J. Engemoen, Jr.
    Title: Chairman

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