EXHIBIT 10.172
                                                                         
             FOURTH AMENDMENT TO LETTER OF CREDIT AGREEMENT

          FOURTH  AMENDMENT TO LETTER OF CREDIT AGREEMENT,  dated  as  of
January  21,  1999  (this "Amendment"), among R&B FALCON  CORPORATION,  a
Delaware corporation (the "Obligor") and CHRISTIANIA BANK OG KREDITKASSE,
NEW  YORK BRANCH (the "Bank").  All capitalized terms used herein and not
otherwise defined shall have the meanings provided such terms in the  L/C
Agreement.

                                    
                          W I T N E S S E T H :
                                    
                                    
          WHEREAS,  the Obligor and the Bank are parties to a  Letter  of
Credit Agreement, dated as of December 30, 1996 (as amended to date,  the
"L/C Agreement"); and

          WHEREAS, the parties hereto wish to amend the L/C Agreement  as
herein provided;

          NOW, THEREFORE, it is agreed:

I.  Amendments to L/C Agreement.

          1.   Section 7.01 of the L/C Agreement is hereby amended by (i)
deleting  the  word  "and"  at  the  end  of  clause  (g)  thereof,  (ii)
redesignating  clause  (h)  thereof as clause (i),  (iii)  inserting  the
following new clause (h) immediately following clause (g) thereof:

          (h)   Indebtedness of the Obligor (including any extensions  or
     refinancing thereof, provided that any such refinancing or extension
     does   not  increase  the  principal  amount  thereof  beyond   that
     outstanding  on  the  date of such extension  or  refinancing),  the
     proceeds  of  which  are  used solely to discharge  indebtedness  of
     Cliffs Drilling under the 10.25% senior notes of Cliffs Drilling due
     2003,  and  in  an  aggregate principal amount not  to  exceed  that
     necessary  to  discharge the portion of such notes  required  to  be
     redeemed  pursuant to the offer to repurchase made pursuant  to  the
     Cliffs  Acquisition; provided that such Indebtedness (or refinancing
     thereof,  as the case may be) shall (i) be unsecured and subordinate
     to  the  Loans and (ii) shall have a maturity date not earlier  than
     one  year after the Maturity Date (as such term is defined from time
     to  time), except that such maturity may occur earlier if and to the
     extent  such  maturity  results solely in  the  conversion  of  such
     Indebtedness  into,  or  exchange for,  other  Indebtedness  of  the
     Obligor,  in the same aggregate principal amount, which is unsecured
     and  subordinated to the Loans and has a maturity date  not  earlier
     than  one year after the Maturity Date (as such term is defined from
     time to time); and
     
, and  (iv) deleting clause (f) thereof in its entirety and inserting the
following new clause (f) in lieu thereof :

          (f)  Indebtedness of Cliffs Drilling acquired pursuant  to  the
     Cliffs  Acquisition  (including any loans made  pursuant  to  unused
     revolving  commitments)  in an aggregate  principal  amount  not  to
     exceed  $235,000,000,  provided  that  (i)  such  Indebtedness   (or
     commitments,  as  the  case  may be) existed  at  the  time  of  the
     consummation  of  the  Cliffs Acquisition and  was  not  created  in
     contemplation thereof (and the provisions thereof were  not  altered
     in  any material respect in contemplation thereof), (ii) the Obligor
     has no liability with respect to any such Indebtedness and (iii) any
     Liens  securing such Indebtedness apply only to the assets of Cliffs
     Drilling  acquired  pursuant  to  the  Cliffs  Acquisition  (and  no
     additional  assets  are  granted  as  security  following,   or   in
     contemplation  of,  the Cliffs Acquisition), and  any  extension  or
     refinancing  of such Indebtedness, provided that such  extension  or
     refinancing  (x)  does  not increase the principal  amount  of  such
     Indebtedness above the outstanding amount thereof immediately  prior
     to  giving effect to such refinancing, (y) does not have a  maturity
     date prior to one year after the Maturity Date (as defined from time
     to  time)  and  (z)  is not secured by any assets not  securing  the
     Indebtedness to be refinanced; and
     
          2.   Section 7.06 of the L/C Agreement is hereby amended by (i)
deleting  the word "and" appearing at the end of clause (c)  thereof  and
inserting  a  comma in lieu thereof and (ii) inserting the following  new
clause  (e)  immediately prior to the period at the  end  of  clause  (d)
thereof:

     and  (e)  so long as no Default or Event of Default then  exists  or
     would  result immediately after giving effect thereto,  the  Obligor
     may  pay  dividends  on its preferred stock not  to  exceed  a  rate
     commensurate with a 10% coupon on such preferred stock.
     
          3.   Section  7.09  of the L/C Agreement is hereby  amended  by
deleting  said  section in its entirety and inserting the  following  new
Section 7.09 in lieu thereof:

          7.09.  Tangible Net Worth.  The Obligor will not permit at  any
     time  its  Tangible Net Worth to be less than $600,000,000 plus  (i)
     50%  of its cumulative Consolidated Net Income, if positive, for the
     period from April 1, 1998 through the date of calculation, plus (ii)
     100%  of any equity issued by the Obligor after the Effective  Date;
     provided  that  ,  for  purposes of this Section  7.09,  the  Cliffs
     Acquisition  shall  be  deemed to constitute  the  issuance  by  the
     Obligor  of  equity  in  an amount equal  to  the  increase  in  the
     Obligor's Tangible Net Worth resulting from the Cliffs Acquisition.
     
          4.   Section  7  of  the  L/C Agreement is  hereby  amended  by
inserting the following new Section 7.13:

          Section  7.13   Restriction  on  Certain  Debt  Payments.   The
     Obligor  shall  not  repay  any indebtedness  incurred  pursuant  to
     Section 7.01(h) except out of net proceeds from the issuance by  the
     Obligor  of  (i) capital stock permitted to be issued  hereunder  or
     (ii) refinancing Indebtedness permitted pursuant to Section 7.01(h);
     provided  that, so long as no Default or Event of Default exists  or
     would  result immediately after giving effect to such payment,  this
     Section 7.13 shall not be deemed to prevent the Obligor from  making
     regularly   scheduled   payments  of  accrued   interest   on   such
     Indebtedness.
     
          5.  Annex 7.01 of the L/C Agreement is hereby amended by adding
thereto the following item:

          "20.  Guaranty by R&B dated as of November 28, 1995 in favor of
          Deep  Sea Investors, L.L.C. with respect to the obligations  of
          Reading  & Bates Drilling Co. under the Memorandum of Agreement
          and  a  charter  as  of  the  same date  with  respect  to  the
          semisubmersible drilling unit M.G Hulme."
          
          6.   Annex  V of the L/C Agreement is hereby amended by  adding
thereto the following item:

         "12.   Preferred  Mortgage on the Jim Cunningham dated  November
         28,  1995  between Reading & Bates Drilling Co.  and  Wilmington
         Trust  Company,  as  Trustee,  for  the  benefit  of  Deep   Sea
         Investors,  L.L.C.,  in  connection with  item  20  of  Schedule
         7.01."
         

II  Miscellaneous Provisions.

          1.   In  order to induce the Bank to enter into this Amendment,
the Obligor hereby represents and warrants that:

          (a)   no  Default or Event of Default exists as of  the  Fourth
     Amendment Effective Date both before and after giving effect to this
     Amendment; and
     
          (b)  all of the representations and warranties contained in the
     L/C Agreement and the other Credit Documents are true and correct in
     all  material respects on the Fourth Amendment Effective  Date  both
     before  and  after giving effect to this Amendment,  with  the  same
     effect  as though such representations and warranties had been  made
     on  and  as  of  the  Fourth  Amendment  Effective  Date  (it  being
     understood that any representation or warranty made as of a specific
     date  shall be true and correct in all material respects as of  such
     specific date).
     
          2.   This  Amendment  is  limited as specified  and  shall  not
constitute a modification, acceptance or waiver of any other provision of
the L/C Agreement or any other Credit Document.

          3.    This   Amendment  may  be  executed  in  any  number   of
counterparts and by the parties hereto on separate counterparts, each  of
which counterparts when executed and delivered shall be an original,  but
all  of  which shall together constitute one and the same instrument.   A
complete  set  of counterparts shall be lodged with the Obligor  and  the
Bank.

          4.   THIS  AMENDMENT  AND  THE RIGHTS AND  OBLIGATIONS  OF  THE
PARTIES HERETO SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY  THE
LAW OF THE STATE OF NEW YORK.

          5.   This  Amendment shall become effective on  the  date  (the
"Fourth Amendment Effective Date") when each of the Obligor and the  Bank
shall  have  signed a counterpart hereof (whether the same  or  different
counterparts)  and shall have delivered (including by  way  of  facsimile
transmission) the same to the Bank at its Notice Office.

          6.   From  and after the Fourth Amendment Effective  Date,  all
references in the L/C Agreement and each of the other Credit Documents to
the  L/C  Agreement shall be deemed to be references to the L/C Agreement
as amended hereby.

          IN WITNESS WHEREOF, the parties hereto have caused their duly
authorized officers to execute and deliver this Amendment as of the date
first above written.

                              R&B FALCON CORPORATION
                              
                              
                              By:_________________________
                                    Title:
                              
                              
                              CHRISTIANIA BANK OG KREDITKASSE, NEW YORK
                              BRANCH
                              
                              
                              By:_________________________
                                    Title:
                              
                              By:_________________________
                                    Title: