A retrospective analysis of the case records of 494 patients with 508 episodes of pneumococcal infections verified by cultures from blood or from cerebrospinal, pleural, and/or synovial fluid from 1964 through 1980 is presented and discussed in relation to the literature on invasive pneumococcal infections. The documented incidence (1976-1980) of pneumococcal meningitis in a defined area of southwestern Sweden was similar to that reported from the United States; 1.4 cases per 100,000 persons per year; for nonmeningitic infections (mainly bacteremic pneumonia) the incidence was 6.1 per 100,000 per year. The highest age-specific incidence was seen in infants younger than two years. In the vast majority of patients, predisposing conditions (young or old age or severe underlying diseases) were present. In adults, alcoholism was the most important risk factor. The fatality rate was 33% for patients with meningitis and 15% for patients with non-meningitic infections, figures that were strikingly similar to those reported in other studies. Underlying diseases and young or old age contributed significantly to the high mortality rates.