The study is based on 333 cerebrospinal fluid (CSP) samples from patients with clinical diagnosis of acute bacterial meningites. The aim of the study is a critical evaluation on latex agglutination tests in CSF for H. influenzae type b, N. meningitidis A and C, and S. pneumoniae. These tests are compared with direct examination (Gram method), and culture results. It was shown that results of the latex test in the CSF are basic for rapid diagnosis of etiological agent in a bacterial meningitis. Data on 106 CSF samples confirmed the etiology through latex tests in 98.2% for H. influenzae type b, in 15.8% for N. meningitidis A or C, in 96.8% for S. pneumoniae. Emphasis is given for evidence of antibiotic therapy previous to CSF collection, which may be responsible for the great number of negative results registered in the present series.