The medical records on all cases of pneumococcal bacteremia in adults at the University Hospital, Leiden, over a 10-year period (1976-1986) were retrospectively reviewed. In this series of 147 episodes (an annual incidence of 0.8 episodes/10,000 adults), overall mortality was 25.9%. Factors significantly related to a higher mortality rate were shock, respiratory insufficiency, preexisting renal failure, and rapidly fatal underlying disease. Several laboratory abnormalities-such as a low percentage of band forms, an elevated level of serum lactate dehydrogenase, and hyperbilirubinemia-were significantly related to a poor outcome. Multilobar pneumonia and meningitis were both associated with high mortality, although not to a statistically significant degree. Discriminant analysis showed the presence of shock as the most powerful predictive factor of death. Surprisingly, prior splenectomy did not correlate with higher mortality. Treatment with beta-lactam antibiotics favorably influenced the outcome of illness in patients with ultimately fatal and nonfatal underlying disease, while the use of these agents in patients with rapidly fatal underlying disease did not correlate significantly with a good prognosis.