The authors emphasize the dangers of diagnostic errors in the cases of neuroblastomycosis, whether in the meningoencephalic or the tumoral forms. Paracoccidioidosis and cryptococcosis are studied. After a clinical characterization of paracoccidioidosis, the authors stress the scarceness of its nervous forms (1,2 per cent of 84 necropsies of this mycosis performed at the Department of Pathology of the Faculty of Medicine of São Paulo). In the literature there are but 12 cases reported. Casiello and Class' is the only case where the diagnosis was made during life; the other cases were necroscopic findings or unexpected histopathologic data after the patients had been operated on por presumptive tumors. The authors report 2 cases of paracoccidioidosis of the nervous system. In the first one, showing meningo-myelo-radiculitis, the parasite was identified in the sputum; the second patient exhibited a syndrome of spinal compression, whose pathogeny is discussed by the authors (lymphatic infiltration of the epidural cervical space? lymphatic infiltration of the spinal cord? allergic diffuse serous inflammation of the spinal cord caused by the ganglionar focus?) ; the paracoccidioidal etiology was attested by bactériologie examination and biopsy of cervical lymph nodes. After clinical comments on cryptococcosis, the authors report a case of subacute meningoencephalomyelitis, which was diagnosed as paracoccidioidal by the mycologie examination of the cerebrospinal fluid; this patient, although treated with high doses of sulfonamides and thiosemicarbarsone, died after two remissions of the symptomatology; the necroscopic examination disclosed the real nature of the neurological changes, which were diagnosed as torular granuloma. In all cases the neurosurgical aspect of the symptomatology was impressive. Neverthless, the diagnosis of paracoccidioidosis imposed the treatment with sulfadiazine, sulfamerazine, specific vaccine and thiosemicarbarsone. Results were remarkable in case 2, where treatment was earlier started; case 1 also showed improvement. In case 3, transient improvement followed the treatment, but, after two years of disease, the patient died. The authors conclude that nervous blastomycosis must be taken on account in neurosurgical considerations. In paracoccidioidosis massive doses of sulfa drugs associated to specific vaccine, however, will be the first therapeutic approach. In the treatment of cryptococcosis streptothricin and actidione are worth trying according to experimental studies. Surgery is indicated only in the cases where the site or developmental conditions of the disease demand urgent resolution.