We report the results of a multicenter tunisian study, performed over a two-year period (1998-1999), to determine the susceptibility pattern of Streptococcus pneumoniae in our country. A total of 146 S. pneumoniae were collected during the study period. 76 were recovered from adults and 70 from children. 53% of isolates have decreased susceptibility to penicillin, 24% with low level resistance, and 11% with high level resistance. Amoxicillin and cefotaxime decreased susceptibility rates were: 12% (low level resistance exclusively). and 14% (10% with low level resistance and 4% with high level resistance) respectively. Strains isolated from children, showed higher resistance to b lactams than those isolated from adults. Resistance rates to other antibiotics were as follow: erythromycin 28%, choramphenicol 14%, cyclins 23%, thrimethoprim-sulfamethoxazole 28% and rifampin 1%. No vancomycin resistant strain was found. The acquire resistance rates of Streptococcus pneumoniae in Tunisia are worrying, essentially for penicillin and erythomycin. Amoxicillin and cefotaxime have conserved a good activity.