Seven of 23 hypertensive patients treated with captopril (SQ 14,225), an orally active converting enzyme inhibitor, developed a pruritic, erythematous, macular, and papular eruption of the trunk, face, and proximal extremities. The eruption appeared one to 31 weeks after initiation of captopril therapy and was associated with diarrhea (three patients), fever (two patients), and generalized arthralgias (one patient). Six patients had an increased percentage of band cells (5 to 34 per cent) on peripheral smear without an associated leukocytosis. In one patient, the skin rash was associated with a peripheral eosinophilia (20 per cent). Coombs-positive hemolytic anemia, and acute renal failure with eosinophiluria. There were no changes in BUN, creatinine, or urinalyses in the remaining patients. Four patients showed a transient rise in plasma PGE without concomitant changes in plasma PFG2 alpha or 6-keto PGF1 alpha, and three patients had slight elevations in the erythrocyte sedimentation rate. Skin biopsies revealed a perivascular and perifollicular lymphocytic and histiocytic infiltrate with negative immunofluorescence to IgG, IgM, IgA, and beta 1 C. The skin eruption and associated symptoms resolved in all patients, even though captopril administration was continued in six of the seven patients.