Objectives: The objective of the study was to determine prevalent pneumococcal serotypes causing infections in different age groups, their susceptibility to fi-lactams and macrolides and whether these serotypes are covered by the conjugated pneumococcal vaccines. Methods: Streptococcus pneumonia strains isolated from different patients at Hamad Medical Corporation, Microbiology Laboratory between September 1999 and July 2000 were sent to Statum Serum Institute in Denmark for serotyping. The strains were tested for their susceptibility to penicillin, ceftriaxone and erythromycin by Vitek 2 machine (bioMerieux, France) at Hamad Medical Corporation, Microbiology Laboratory. Results: Predominant serotypes in children <  2 years were: 6A, 6B, 9V, 11 A, 14,19A, 19F and 23 F, predominant serotypes in children between 2-7years were: 3, 6B, 15B, 19A, 19F and 23F, while predominant serotypes in adults were: 3, 8, 9V, 14,15B, 20 and 22F. In children less than 2 years, the 7-valent and 9-valent conjugate vaccines covered 52% of serotypes. 33% of strains were moderately resistant to penicillin, 27% showed high-level resistance to penicillin, 30% resistant to erythromycin and 2% resistant to ceftrixone. Conclusion: The 7-valent and 9-valent vaccines offer similar coverage of serotypes in children less than 2 years while the 11-valent vaccines offers 55% coverage. This difference is not statistically significant. Resistance to penicillin was high which leaves ceftriaxone as the drug of choice for empirical treatment of invasive pneumococcal diseases.