FLOATING RATE JUNIOR SUBORDINATED DEFERRABLE INTEREST DEBENTURE

                                     [COPY]

         THIS SECURITY IS NOT A SAVINGS ACCOUNT OR DEPOSIT AND IT IS NOT INSURED
BY THE UNITED STATES OR ANY AGENCY OR FUND OF THE UNITED  STATES,  INCLUDING THE
FEDERAL DEPOSIT INSURANCE CORPORATION.

         THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
AS  AMENDED  (THE  "SECURITIES  ACT"),  ANY STATE  SECURITIES  LAWS OR ANY OTHER
APPLICABLE   SECURITIES   LAW.   NEITHER  THIS  SECURITY  NOR  ANY  INTEREST  OR
PARTICIPATION  HEREIN MAY BE REOFFERED,  SOLD, ASSIGNED,  TRANSFERRED,  PLEDGED,
ENCUMBERED  OR  OTHERWISE  DISPOSED  OF IN THE ABSENCE OF SUCH  REGISTRATION  OR
UNLESS SUCH  TRANSACTION  IS EXEMPT  FROM,  OR NOT SUBJECT TO, THE  REGISTRATION
REQUIREMENTS OF THE SECURITIES ACT AND ANY APPLICABLE STATE SECURITIES LAWS. THE
HOLDER OF THIS  SECURITY  BY ITS  ACCEPTANCE  HEREOF  AGREES  TO OFFER,  SELL OR
OTHERWISE  TRANSFER  THIS  SECURITY  ONLY (A) TO THE COMPANY,  (B) PURSUANT TO A
REGISTRATION  STATEMENT THAT HAS BEEN DECLARED  EFFECTIVE  UNDER  THE SECURITIES
ACT,  (C) TO A  PERSON  WHOM  THE  SELLER  REASONABLY  BELIEVES  IS A  QUALIFIED
INSTITUTIONAL  BUYER IN A TRANSACTION  MEETING THE  REQUIREMENTS OF RULE 144A SO
LONG AS THIS SECURITY IS ELIGIBLE FOR RESALE PURSUANT TO RULE 144A IN ACCORDANCE
WITH  RULE  144A,  (D)  TO A  NON-U.S.  PERSON  IN AN  OFFSHORE  TRANSACTION  TN
ACCORDANCE  WITH RULE 903 OR RULE 904 (AS  APPLICABLE) OF REGULATION S UNDER THE
SECURITIES ACT, (E) TO AN INSTITUTIONAL "ACCREDITED INVESTOR" WITHIN THE MEANING
OF SUBPARAGRAPH (A) OF RULE 501  UNDER THE SECURITIES ACT THAT IS ACQUIRING THIS
SECURITY  FOR  ITS OWN  ACCOUNT,  OR FOR THE  ACCOUNT  OF SUCH AN  INSTITUTIONAL
ACCREDITED  INVESTOR,  FOR  INVESTMENT  PURPOSES  AND NOT WITH A VIEW TO, OR FOR
OFFER  OR  SALE  IN  CONNECTION  WITH,  ANY  DISTRIBUTION  IN  VIOLATION  OF THE
SECURITIES  ACT,  OR (F)  PURSUANT  TO ANY OTHER  AVAILABLE  EXEMPTION  FROM THE
REGISTRATION  REQUIREMENTS OF THE SECURITIES ACT, SUBJECT TO THE COMPANY'S RIGHT
PRIOR TO ANY SUCH OFFER,  SALE OR TRANSFER TO REQUIRE THE DELIVERY OF AN OPINION
OF  COUNSEL,  CERTIFICATION  AND/OR  OTHER  INFORMATION  SATISFACTORY  TO  IT IN
ACCORDANCE WITH THE INDENTURE, A COPY OF WHICH MAY BE OBTAINED FROM THE COMPANY.


         THE HOLDER OF THIS  SECURITY  BY ITS  ACCEPTANCE  HEREOF  ALSO  AGREES,
REPRESENTS  AND  WARRANTS  THAT  IT  IS  NOT  AN  EMPLOYEE  BENEFIT,  INDIVIDUAL
RETIREMENT  ACCOUNT  OR  OTHER  PLAN OR  ARRANGEMENT  SUBJECT  TO TITLE I OF THE
EMPLOYEE  RETIREMENT  INCOME  SECURITY  ACT OF 1974,  AS AMENDED  ("ERISA"),  OR
SECTION 4975 OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE") (EACH
A "PLAN"),  OR AN ENTITY WHOSE UNDERLYING ASSETS INCLUDE "PLAN ASSETS" BY REASON
OF ANY PLAN'S INVESTMENT IN THE ENTITY, AND NO PERSON INVESTING "PLAN ASSETS" OF
ANY PLAN MAY ACQUIRE OR HOLD THE SECURITIES OR ANY INTEREST THEREIN, UNLESS SUCH
PURCHASER  OR HOLDER IS  ELIGIBLE  FOR  EXEMPTIVE  RELIEF  AVAILABLE  UNDER U.S.
DEPARTMENT OF LABOR PROHIBITED  TRANSACTION CLASS EXEMPTION 96-23, 95-60, 91-38,
90-1 OR 84-14 OR ANOTHER  APPLICABLE  EXEMPTION  OR ITS  PURCHASE AND HOLDING OF
THIS  SECURITY IS NOT  PROHIBITED BY SECTION 406 OF ERISA OR SECTION 4975 OF THE
CODE WITH RESPECT TO SUCH  PURCHASE OR HOLDING.  ANY  PURCHASER OR HOLDER OF THE
SECURITIES  OR ANY INTEREST  THEREIN WILL BE DEEMED TO HAVE  REPRESENTED  BY ITS
PURCHASE AND HOLDING THEREOF THAT EITHER (i) IT IS NOT AN EMPLOYEE  BENEFIT PLAN
WITHIN THE MEANING OF SECTION 3(3) OF ERISA,  OR A PLAN TO WHICH SECTION 4975 OF
THE CODE IS  APPLICABLE,  A  TRUSTEE  OR OTHER  PERSON  ACTING  ON  BEHALF OF AN
EMPLOYEE BENEFIT PLAN OR PLAN, OR ANY OTHER PERSON OR ENTITY USING THE ASSETS OF
ANY  EMPLOYEE  BENEFIT  PLAN OR PLAN TO  FINANCE  SUCH  PURCHASE,  OR (ii)  SUCH
PURCHASE WILL NOT


                                        1
<PAGE>

RESULT IN A PROHIBITED TRANSACTION UNDER SECTION 406 OR ERISA OR SECTION 4975 OF
THE CODE FOR WHICH THERE IS NO APPLICABLE STATUTORY OR ADMINISTRATIVE EXEMPTION.

         THIS  SECURITY  WILL BE ISSUED  AND MAY BE  TRANSFERRED  ONLY IN BLOCKS
HAVING AN AGGREGATE  PRINCIPAL AMOUNT OF NOT LESS THAN $500,000.00 AND MULTIPLES
OF $1,000.00 IN EXCESS  THEREOF.  ANY  AITEMPTED  TRANSFER OF THIS SECURITY IN A
BLOCK HAVING AN AGGREGATE  PRINCIPAL  AMOUNT OF LESS THAN  $500,000.00  SHALL BE
DEEMED TO BE VOID AND OF NO LEGAL EFFECT WHATSOEVER.

         THE  HOLDER  OF THIS  SECURITY  AGREES  THAT IT WILL  COMPLY  WITH  THE
FOREGOING RESTRICTIONS.

         IN  CONNECTION  WITH ANY  TRANSFER,  THE  HOLDER  WILL  DELIVER  TO THE
REGISTRAR AND TRANSFER AGENT SUCH  CERTIFICATE  AND OTHER  INFORMATION AS MAY BE
REQUIRED  BY THE  INDENTURE  TO  CONFIRM  THAT THE  TRANSFER  COMPLIES  W1TH THE
FOREGOING RESTRICTIONS.

         Floating Rate Junior Subordinated Deferrable Interest Debenture

                                       of

                                North Bay Bancorp

                                  June 26, 2002

          North Bay Bancorp, a California  corporation (the "Company" which term
includes any successor Person under the Indenture  hereinafter referred to), for
value  received  promises  to pay to State  Street  Bank and  Trust  Company  of
Connecticut,  National Association, not in its individual capacity but solely as
Institutional  Trustee  for  North  Bay  Statutory  Trust  I (the  "Holder")  or
registered assigns,  the principal sum of ten million three hundred ten thousand
dollars ($10,310,000.00) on June 26, 2032, and to pay interest on said principal
sum from June 26, 2002, or from the most recent interest payment date (each such
date,  an  "Interest  Payment  Date")  to which  interest  has been paid or duly
provided for,  quarterly (subject to deferral as set forth herein) in arrears on
March  26,  June  26,  September  26 and  December  26 of each  year  commencing
September  26,  2002,  at an annual  rate  equal to 5.3369%  beginning  on  (and
including) the date of original issuance and ending on (but excluding) September
26,  2002 and at an annual rate for each  successive  period  beginning  on (and
including)  September 26, 2002, and each succeeding  Interest  Payment Date, and
ending on (but  excluding)  the next  succeeding  Interest  Payment Date (each a
"Distribution  Period"),  equal to 3-Month LIBOR, determined as described below,
plus 3.45% (the "Coupon Rate"); provided,  however, that prior to June 26, 2007,
the Coupon Rate shall not exceed 11.95%, applied to the principal amount hereof,
until the principal  hereof is paid or duly  provided for or made  available for
payment,  and on any overdue principal and (without  duplication) on any overdue
installment of interest at the same rate per annum,  compounded quarterly,  from
the  dates  such  amounts  are due  until  they are paid or made  available  for
payment.  The amount of interest  payable for any period will be computed on the
basis of the actual number of days in the Distribution  Period concerned divided
by 360.  In the  event  that any  date on  which  interest  is  payable  on this
Debenture is not a Business Day, then a payment of the interest  payable on such
date  will be made on the  next  succeeding  day  which is a  Business  Day (and
without any  interest  or other  payment in respect of any such  delay),  except
that, if such Business Day is in the next succeeding calendar year, such payment
shall be made on the immediately  preceding  Business Day, in each case with the
same force and effect as if made on the date the payment was originally payable.
The interest  installment so payable,  and punctually paid or duly provided for,
on any Interest Payment Date will, as provided in the Indenture,  be paid to the
Person in whose name this Debenture (or one or more  Predecessor  Securities) is
registered at the close of business on the regular record date for such interest
installment, which shall be fifteen days prior to the day on which the relevant


                                        2
<PAGE>

Interest  Payment Date occurs.  Any such interest  installment not so punctually
paid or duly provided for shall  forthwith  cease to be payable to the Holder on
such  regular  record  date and may be paid to the  Person  in whose  name  this
Debenture (or one or more Predecessor  Securities) is registered at the close of
business on a special record date.

          "3-Month  LIBOR" as used herein,  means the London  interbank  offered
interest rate for three-month U.S. dollar deposits  determined by the Trustee in
the following  order of priority:  (i) the rate  (expressed as a percentage  per
annum) for U.S. dollar  deposits  having a three-month  maturity that appears on
Telerate Page 3750 as of 11:00 a.m.  (London time) on the related  Determination
Date  ("Telerate  Page 3750" means the display  designated as "Page 3750" on the
Dow Jones  Telerate  Service or such other page as may replace Page 3750 on that
service or such other  service or  services as may be  nominated  by the British
Bankers'  Association  as the  information  vendor for the purpose of displaying
London  interbank  offered rates for U.S.  dollar  deposits);  (ii) if such rate
cannot be identified on the related Determination Date, the Trustee will request
the  principal  London  offices of four  leading  banks in the London  interbank
market to provide such banks' offered  quotations  (expressed as percentages per
annum) to prime banks in the London  interbank  market for U.S.  dollar deposits
having  a  three-month   maturity  as  of  11:00  a.m.  (London  time)  on  such
Determination Date. If at least two quotations are provided,  3-Month LIBOR will
be the  arithmetic  mean of such  quotations;  (iii)  if  fewer  than  two  such
quotations  are  provided as  requested  in clause (ii) above,  the Trustee will
request four major New York City banks to provide such banks' offered quotations
(expressed as percentages per annum) to leading European banks for loans in U.S.
dollars as of 11:00 a.m. (London time) on such  Determination  Date. If at least
two such  quotations are provided,  3-Month LIBOR will be the arithmetic mean of
such  quotations;  and (iv) if fewer than two such  quotations  are  provided as
requested  in  clause  (iii)  above,  3-Month  LIBOR  will  be a  3-Month  LIBOR
determined with respect to the Distribution  Period  immediately  preceding such
current  Distribution  Period.  If the rate for U.S.  dollar  deposits  having a
three-month  maturity that  initially  appears on Telerate Page 3750 as of 11:00
a.m.  (London  time) on the  related  Determination  Date is  superseded  on the
Telerate  Page 3750 by a  corrected  rate by 12:00  noon  (London  time) on such
Determination  Date, then the corrected rate as so substituted on the applicable
page will be the applicable 3-Month LIBOR for such  Determination  Date. As used
herein,  "Determination  Date"  means the date that is two London  Banking  Days
(i.e.,  a  business  day in which  dealings  in  deposits  in U.S.  dollars  are
transacted in the London  interbank  market)  preceding the  commencement of the
relevant Distribution Period.

          The Coupon Rate for any Distribution  Period will at no time be higher
than the maximum rate then permitted by New York law as the same may be modified
by United States law.

          All percentages resulting from any calculations on the Debentures will
be rounded, if necessary,  to the nearest one hundred-thousandth of a percentage
point,  with five  one-millionths  of a percentage  point rounded  upward (e.g.,
9.876545% or  .09876545  being  rounded to 9.87655% or .0987655,  and all dollar
amounts  used in or  resulting  from such  calculation  will be  rounded  to the
nearest cent (with one-half cent being rounded upward)).

          The  principal of and interest on this  Debenture  shall be payable at
the office or agency of the  Trustee (or other  paying  agent  appointed  by the
Company)  maintained  for that  purpose  in any coin or  currency  of the United
States of America  that at the time of payment  is legal  tender for  payment of
public and private  debts;  provided,  however,  that payment of interest may be
made by check mailed to the registered holder at such address as shall appear in
the  Debenture  Register if a request for a wire transfer by such holder has not
been  received  by the Company or by wire  transfer to an account  appropriately
designated by the holder hereof.  Notwithstanding the foregoing,  so long as the
holder of this  Debenture  is the  Institutional  Trustee,  the  payment  of the
principal  of and  interest  on this  Debenture  will  be  made  in  immediately
available  funds at such place and to such account as may be  designated  by the
Trustee.

          So long as no Event of Default has  occurred  and is  continuing,  the
Company shall have the right, from time to time, and without causing an Event of
Default, to defer payments of interest on the Debentures by


                                        3
<PAGE>

extending  the interest  payment  period on the  Debentures at any time and from
time  to  time  during  the  term of the  Debentures,  for up to 20  consecutive
quarterly  periods (each such extended  interest  payment period,  an "Extension
Period"),  during  which  Extension  Period no  interest  (including  Additional
Interest) shall be due and payable.  No Extension Period may end on a date other
than an  Interest  Payment  Date.  At the end of any such  Extension  Period the
Company  shall pay all  interest  then  accrued  and  unpaid  on the  Debentures
(together  with  Additional  Interest  thereon);   provided,  however,  that  no
Extension Period may extend beyond the Maturity Date; provided further, however,
that  during any such  Extension  Period,  the  Company  shall not and shall not
permit any Affiliate to (i) declare or pay any dividends or distributions on, or
redeem, purchase, acquire, or make a liquidation payment with respect to, any of
the  Company's  or such  Affiliate's  capital  stock  (other  than  payments  of
dividends or distributions  to the Company) or make any guarantee  payments with
respect to the foregoing or (ii) make any payment of principal of or interest or
premium,  if any, on or repay,  repurchase or redeem any debt  securities of the
Company or any Affiliate  that rank pari passu in all respects with or junior in
interest to the  Debentures  (other  than,  with respect to clauses (i) and (ii)
above, (a) repurchases,  redemptions or other  acquisitions of shares of capital
stock of the Company in connection with any employment contract, benefit plan or
other  similar  arrangement  with or for the  benefit of one or more  employees,
officers,  directors or consultants,  in connection with a dividend reinvestment
or stockholder stock purchase plan or in connection with the issuance of capital
stock of the Company (or securities  convertible  into or  exercisable  for such
capital stock) as consideration in an acquisition transaction entered into prior
to the applicable Extension Period, (b)as a result of any exchange or conversion
of any class or series of the Company's capital stock (or any capital stock of a
subsidiary  of the  Company)  for any class or series of the  Company's  capital
stock or of any class or series of the Company's  indebtedness  for any class or
series of the Company's capital stock, (c) the purchase of fractional  interests
in shares of the Company's  capital stock pursuant to the conversion or exchange
provisions of such capital stock or the security  being  converted or exchanged,
(d) any  declaration of a dividend in connection with any  stockholders'  rights
plan, or the issuance of rights, stock or other property under any stockholders'
rights plan, or the redemption or repurchase of rights pursuant thereto, (e) any
dividend  in the form of stock,  warrants,  options  or other  rights  where the
dividend stock or the stock issuable upon exercise of such warrants,  options or
other  rights is the same stock as that on which the  dividend  is being paid or
ranks pari passu with or junior to such stock and any cash  payments  in lieu of
fractional  shares issued in  connection  therewith,  or (f) payments  under the
Capital Securities Guarantee). Prior to the termination of any Extension Period,
the Company may further extend such period,  provided that such period  together
with all such  previous and further  consecutive  extensions  thereof  shall not
exceed 20  consecutive  quarterly  periods,  or extend beyond the Maturity Date.
Upon the termination of any Extension Period and upon the payment of all accrued
and unpaid  interest  and  Additional  Interest,  the Company may commence a new
Extension  Period,  subject  to  the  foregoing  requirements.  No  interest  or
Additional Interest shall be due and payable during an Extension Period,  except
at the end thereof,  but each  installment of interest that would otherwise have
been  due and  payable  during  such  Extension  Period  shall  bear  Additional
Interest.  The Company must give the Trustee  notice of its election to begin or
extend such  Extension  Period at least 5 Business  Days prior to the earlier of
(i) the date interest on the  Debentures  would have been payable except for the
election  to begin  such  Extension  Period  or (ii) the date such  interest  is
payable,  but in any event not less than 5 Business  Days  prior to such  record
date.

          This  Debenture  is one  of  the  floating  rate  junior  subordinated
deferrable interest debentures of the Company,  all issued or to be issued under
and  pursuant to the  Indenture  dated as of June 26,  2002,  duly  executed and
delivered between the Company and the Trustee,  to which Indenture  reference is
hereby made for a description of the rights, limitations of rights, obligations,
duties and immunities  thereunder of the Trustee, the Company and the holders of
the  Debentures.  The  Debentures are limited in aggregate  principal  amount as
specified in the Indenture.

          The  indebtedness  evidenced  by  this  Debenture  is,  to the  extent
provided  in the  Indenture,  subordinate  and junior in right of payment to the
prior payment in full of all Senior  Indebtedness,  and this Debenture is issued
subject to the provisions of the Indenture with respect thereto.  Each holder of
this


                                        4
<PAGE>

Debenture,  by  accepting  the  same,  (a)  agrees to and shall be bound by such
provisions,  (b) authorizes and directs the Trustee on his or her behalf to take
such action as may be necessary or  appropriate to acknowledge or effectuate the
subordination  so provided  and (c)  appoints  the  Trustee his or her  attorney
in-fact  for  any and all  such  purposes.  Each  holder  hereof,  by his or her
acceptance   hereof,   hereby  waives  all  notice  of  the  acceptance  of  the
subordination provisions contained herein and in the Indenture by each holder of
Senior Indebtedness,  whether now outstanding or hereafter incurred,  and waives
reliance by each such holder upon said provisions.

          This  Debenture  shall  not be  entitled  to  any  benefit  under  the
Indenture hereinafter referred to, be valid or become obligatory for any purpose
until the certificate of  authentication  hereon shall have been signed by or on
behalf of the Trustee.

          Capitalized  terms used and not defined in this  Debenture  shall have
the meanings assigned in the Indenture dated as of the date of original issuance
of this Debenture between the Trustee and the Company.

          IN WITNESS WHEREOF, the Company has duly executed this certificate.

                                          NORTH BAY BANCORP



                                          By: /s/ Terry L. Robinson
                                             -----------------------------------
                                          Name: Terry L. Robinson
                                          Title: President & CEO


                                                   [COPY]


                          CERTIFICATE OF AUTHENTICATION

          This  is one of the  Debentures  referred  to in the  within-mentioned
Indenture.

                                          State Street Bank and Trust Company of
                                          Connecticut, National Association,
                                          as Trustee


                                          By:    ?????????????????
                                             -----------------------------------
                                                  Authorized Officer


                                                   [COPY]
                                        5