Gram stain, culture and latex agglutination test (LAT) of cerebrospinal fluid were performed in 50 patients clinically diagnosed as suffering from pyogenic bacterial meningitis. Using all the three techniques, an aetiological diagnosis was made in 27 (54%). Neisseria meningitidis, Streptococcus pneumoniae and H. influenzae were the infecting organisms in 21 cases (44%). There were 12 additional cases in which LAT was the only clue to the diagnosis as compared to conventional techniques. Propionibacterium acnes was isolated from one case of anaerobic meningitis. It is concluded that LAT is an adjunct to conventional techniques in the diagnosis of pyogenic bacterial meningitis, where the latter tests fail.