The distribution of pneumococcal serotypes among 465 invasive isolates recovered from 1999 to 2002 in Portugal was analysed by age group. Serotype 14 was either the most prevalent or the second most prevalent in all age groups. Among children aged < 2 years, serotypes 6B and 23F, which are usually associated with children, together with serotypes 19A and 14, accounted for more than half of the isolates. In contrast, in older adults (> or = 60 years), serotypes 3, 14, 1, 8 and 4 were the most prevalent. The potential coverage of the seven-valent conjugate vaccine is 63.2% among infants, and does not change significantly if children aged < 6 years are considered, which is a lower coverage than in other European countries. The potential coverage of the 23-valent polysaccharide vaccine is high in all age groups, particularly among older adults (80.7%). All isolates were tested for their susceptibility to penicillin, cefuroxime, cefotaxime, vancomycin, erythromycin, clindamycin, levofloxacin, gatifloxacin, moxifloxacin, linezolid, quinupristin-dalfopristin, tetracycline, chloramphenicol and trimethoprim-sulphamethoxazole. Most isolates collected from children aged < 6 years had decreased susceptibility to at least one antibiotic class, whereas isolates from patients aged > or = 6 years were mostly susceptible to all antimicrobial agents tested. Overall, 23% of isolates showed reduced susceptibility to penicillin. Most (98.5%) isolates remained fully susceptible to cefotaxime, and a single isolate was resistant to quinolones.