Neurological and cerebro-spinal fluid examinations were made in 55 patients with visceral and/or tegumental South-American blastomycosis in different phases of evolution. Symptoms or signs suggesting involvement of the central nervous system were present in 14 patients; in 5 cases of this last group the examination of the spinal fluid gave data yielding the etiological diagnosis. From the 41 patients that did not present neurological symptomatology, in one of them the spinal fluid gave data of diagnostic value, including the positivity of the mycological search. Twenty three patients were considered normal under the neurological point of view and 26 have shown minor clinical and/or cerebro-spinal fluid alterations without diagnostic value. The author considered as suggestive for the diagnosis the quantitative or qualitative alterations of the proteic fractions of the cerebro-spinal fluid, being particularly important the levels of the gamma-globulin above 20 per cent by paper electrophoresis and the positivity of the complement-fixing reaction with titers above 3. The presence of precipitins in the cerebro-spinal fluid occurred occasionally being not important for the diagnosis or for the evolutive study. It was possible to confirm that the demonstration of the parasite in the cerebro-spinal fluid is rare either by direct examination or by culture. The importance of the clinical-neurological examination of patients with South-American blastomycosis owing to the possibility of existence of subclinical forms of neuroblastomycosis is emphazised.