Cerebrospinal fluid isolates of Streptococcus pneumoniae, collected during the years 1997-2000 at more than 100 Belgian laboratories were studied. The 10 most common serotypes-serogroups representing 76% of the isolates were 14, 6, 9, 19, 23, 18, 4, 10, 8 and 12 (in order of frequency). Thirty-six percent of strains were isolated in children < 5 years old. In this age group the number of serogroups was more limited and 81.4% are included in the 7-valent conjugate vaccine. Decreased susceptibility to penicillin was observed in 13.9% of 237 strains (MIC > 0.06 mg/L), with only 2.1% resistant strains (MIC > 1 mg/L). Twelve strains showed reduced susceptibility to cefotaxime (MIC > 0.5 mg/L). Only three of the 237 strains were intermediately susceptible to meropenem. All strains were susceptible to vancomycin and moxifloxacin. In Belgium, high doses of third generation cephalosporins remain effective for the treatment of pneumococcal meningitis. The new fluoroquinolones seem the most promising agents for the treatment of pneumococcal meningitis in the future.