Retrospective study of bacterial meningitis cases was performed by analysis of filled questionnaires received from 38 different hospitals located in 27 out of 49 provinces of Poland. Obtained data allowed to indicate that S. epidermidis, N. meningitidis, S. pneumoniae and H. influenzae were the most common bacterial strains isolated from cerebrospinal fluid of meningitis patients during the last five years. Besides data analysis performed, some strains of N. meningitidis (n = 97), H. influenzae (n = 28) and S. pneumoniae (n = 39) isolated from cerebrospinal fluid of meningitis patients hospitalized in different places in Poland sent by cooperating hospital laboratories (1995-1996), were phenotypically characterized. Neisseria meningitidis B:22:P1.14 was the most common isolate phenotype during the investigated time period. Streptococcus pneumoniae of twenty different serological types were isolated. Type 1 was the dominant--18% of strains. All but one Haemophilus influenzae strains isolated from cerebrospinal fluid belonged to serological type b. Biotyping showed presence of only two types: I and II, 39.3% and 60.7% of isolates respectively. The sensitivity of collected strains to selected antimicrobial agents (penicillin, cefotaxime, ceftriaxone, sulphametoxazol, chloramphenicol, tetracycline, ciprofloxacin, rifampin and erythromycin) used in treatment and prophylaxis of bacterial meningitis was investigated. Minimum inhibitory concentrations were determined by agar dilution method or with the use of E-tests. All investigated strains but one N. meningitidis, were not resistant to penicillin (MIC < or = 1 microgram/ml).