Exhibit 10(a) DeGolyer and MacNaughton 4925 Greenville Avenue, Suite 400 One Energy Square Dallas, Texas 75206 June 21, 2002 Petroleo Brasileiro S.A. Av. Republica do Chile, 65/1703 Rio de Janeiro--RJ Brasil 20035-900 Gentlemen: We hereby consent to the references to our firm as set forth in the Annual Report on Form 20-F of Petroleo Brasileiro S.A. (Petrobras) for the year ended December 31, 2001. Our estimates of the oil, condensate, and natural gas reserves of certain properties owned by Petrobras are contained in our report entitled "Letter Report as of December 31, 2001 on Reserves of Certain Properties in Brazil with interest owned by Petroleo Brasileiro S.A. SEC Case." Very truly yours, /s/ DeGOLYER and MacNAUGHTON