From January 1st up to September 30th 1990, 77 patients with leptospirosis diagnosis confirmed by laboratory studies were admitted at the Infectious and Parasitic Disease Service of the Hospital das Clínicas of the Universidade Federal de Pernambuco. The neurological exam was abnormal in 70 of the patients (90.91%). The cerebrospinal fluid (CSF) examination was carried out on 67 (87%) of the patients; it was abnormal in 64 (95.52%) yielding hypercytosis in the majority of cases. There was no difference in the CSF behavior in report to the several neurological forms nor in relation to the icteric or non-icteric forms of the disease. Significant were the results for the microscopic agglutination tests for leptospirosis in the CSF.