Twenty-seven cases of South American blastomycosis are reported. Pulmonary lesions predominate and the diagnosis rests on the findings of Paracoccidioides brasiliensis in sputum and tissues. Serological examinations (complement fixation and immunodiffusion) are also useful. Treatment includes sulphonamides, imidazole derivatives and, in cases resistant to these drugs, Amphotericin B. Surgery is limited to abscesses, bone lesions and bronchial stenoses.