The respiratory burst oxidase of phagocytes and B lymphocytes is a complicated enzyme that catalyzes the one-electron reduction of oxygen by NADPH. It is responsible for the O2- production that occurs when these cells are exposed to phorbol 12-myristate 13-acetate or other appropriate stimuli. The activity of this enzyme is greatly decreased or absent in patients with chronic granulomatous disease, an inherited disorder characterized by a severe defect in host defense against bacteria and fungi. In every chronic granulomatous disease patient studied to date, an abnormality has been found in a gene encoding one of four components of the respiratory burst oxidase: the membrane protein p22phox or gp91phox, or the cytosolic protein p47phox or p67phox. We report here that O2- production was partly restored to phorbol 12-myristate 13-acetate-stimulated Epstein-Barr virus-transformed B lymphocytes from a patient with p47phox-deficient chronic granulomatous disease by transfection with an expression plasmid containing a p47phox cDNA inserted in the sense direction. No detectable O2- was produced by untransfected p47phox-deficient lymphocytes or by p47phox-deficient lymphocytes transfected with an antisense plasmid. The finding that O2- can be produced by p47phox-deficient B lymphocytes after the transfer of a p47phox cDNA into the deficient cells suggests that this system could be useful for studying the function of mutant p47phox proteins in whole cells.