Laboratory-based surveillance of invasive pneumococcal infections in adults in Finland from 1983 to 1992 identified 862 episodes of pneumococcal bacteraemia and 97 episodes of meningitis. The overall incidence of invasive pneumococcal infections was 9.1 per 100,000 for all adults per year, but 27.1, 35.8, and 44.5 per 100,000 in those aged 65 years or over, 75 years or over, and 85 years or over, respectively. Most (99.7%) of the pneumococcal strains were sensitive to penicillin. Ninety-five percent of the strains belonged to serogroups/types present in the 23-valent pneumococcal polysaccharide vaccine. Group/type distribution was different in patients aged 16-64 years compared to those 65 years or over (P < 0.001), in bacteraemia compared to meningitis (P < 0.001), and in the years 1983-7 compared to 1988-92 (P < 0.05).