Objective. To obtain etiologic and epidemiologic information about bacterial meningitis, especially the H influenza type B (Hib), from a medium-sized city, Hefei, China. Methods. Data were collected prospectively over 3 years, from 1990 to 1992 by a well-organized group including 13 hospitals. All children with a clinical diagnosis of acute bacterial meningitis were enrolled and the specimens were taken for the etiologic studies. CSF and blood were tested by standard bacteriologic technique. CSF, blood and concentrated urine were tested directly for detection of antigen by countercurrent immuno-electrophoresis (CIE). Data were analyzed by epidemiologic methods. Results. Bacterial culture and CSF Gram's staining were positive only in 13.3% and 11.7%, respectively. Bacterial antigen detection was positive in up to 90% by CIE which was more sensitive than bacterial culture (X(2)=67.7, P<0.005). The annual incidence of acute bacterial meningitis in the city is calculated as 9.3 cases/100 000 children from 1 month to 15 years of age and 19.2 cases/100 000 children from 1 month to 5 years of age. Hib meningitis accounted for 51.7%, N. meningitis (Nm) for 38.3%, and S. pneumoniae (Sp) for 8.3%. There was no significant seasonal variation. Of the patients, 76.7% were children under 5 years of age, and 51.7% under 1 year of age. The case fatality rate was 11.7% for all bacterial meningitis, 9.7% for Hib, 17.4% for Nm and 20% for Sp. A total of 22.6% of survivors suffered from neurological or psychological problems. Conclusions. Using antigen detection combined with bacterial culture, we could make an etiologic diagnosis in up to 90% of the patients in this group. Hib, Nm and Sp were the predominant pathogens, which was similar to the findings in other countries. Hib was the most common cause of bacterial meningitis, but the incidence was much lower than in most parts of the world.