Twelve patients with chronical and sistemic lesions due to paracoccidioidomycosis were treated with Ketoconazole. The treatment lasted for 18 months and the Ketoconazole was ad ministered by oral route, in a once a day do sage of 400 mg during the first month and of 200 mg in the next 17 months. All patients were evaluated in the course of the treatment as well as for 135 days after the end of it, by means of clinical picture, chest X-Ray and serological tests. The immune response was observed in all patients before the treatment and in 4 of them at the end of it. Results showed that there was recrudescence in 5 patients and side effect was observed in only one patient (pruritus). The agar-gel difusion and the sedimentation rate were the laboratorial findings which paralleled the best the clinical picture.