The Bactigen latex agglutination and Phadebact coagglutination tests were evaluated for their ability to detect bacterial antigens of Haemophilus influenzae type b, Streptococcus pneumoniae (83 serotypes) and Neisseria meningitidis groups A, B, C, and Y in 214 samples of cerebrospinal fluid (CSF). Bactigen latex agglutination was more sensitive than Phadebact coagglutination: it detected 87% (59/68) of culture positive CSF specimens, whereas Phadebact detected 72% (52/72). Bactigen detected all cases of meningitis caused by S pneumoniae and H influenzae. Of the 19 specimens that were positive for N meningitidis, 74% were detected by Phadebact and only 53% by Bactigen. Gram stain results were positive for 85% of all specimens positive on culture. Bactigen was slightly more specific (97%) than Phadebact (96%). Bactigen, however, showed less specificity (81%) than Phadebact (94%) on 31 CSF specimens that were culture positive for organisms other than the test organisms. These included two CSF specimens from patients with tuberculous meningitis which gave false positive results for S pneumoniae with the Bactigen reagents. No false positive results were obtained on 104 culture negative CSF samples. Bactigen latex agglutination was superior to Phadebact coagglutination and Gram stain for the detection of S pneumoniae and H influenzae in CSF specimens from patients with bacteriologically proved meningitis.