The results of ketoconazole therapy in 38 patients with active paracoccidioidomycosis are described. Treatment consisted of a 200 mg tablet a day for 6 months. Evaluation was accomplished by means of a scoring system and the results were as follows: none of the patients worsened during therapy, one was found to be unchanged, five had minor improvement, 330 had major improvement, and there was complete resolution of the pretherapy conditions in 13. These findings plus the lack of toxicity of the drug and the facility for oral administration, make of ketoconazole a first line drug for the treatment of paracoccidioidomycosis.