Incidence was the highest each spring. The odds ratio of the case fatality among pneumococcal/lobar pneumonia patients complicated with empyema to those without was 118 (95% confidence interval 28-492). In conclusion, the populationbased incidences of pneumococcal/lobar pneumonia and empyema among children under five in Taiwan were 44.9 and 10.5 episodes per 100,000 children-year, respectively, and 4-to 5-year-old children had the highest incidences of both pneumococcal/lobar pneumonia and empyema. This population might benefit from a universal pneumococcal vaccination program which might cover about 70% of invasive pneumococcal diseases in Taiwanese children under 5 years old.