Empyema rarely complicates pneumonia. In a 361-bed regional pediatric hospital, 50 pleural empyemas were identified from 1988 through 1994; 17 (34%) occurred in the last 12 months of this period, for which the incidence was 3.3 per 100,000 of the population aged < or = 18 years (P < .05, chi 2 test). A significant seasonal prevalence was observed: 50% of cases occurred in the winter (P < .001, chi 2 test). In contrast with the findings of previous studies, in which empyemas predominantly occurred in infants, the median age of our patients was 7 years; underlying illnesses were present in only 10%, and all had community-acquired disease. Eighty-two percent had chest tubes inserted, 56% required a thoracotomy with pleural decortication, and 2% had a lobectomy. There were no deaths. Streptococcus pneumoniae was isolated in 40% of the cases; specimens in 44% of the cases were sterile. None of the empyemas were associated with Staphylococcus aureus or Haemophilus influenzae type b, and only one was caused by group A streptococcus. Among 13 S. pneumoniae isolates, the rate of resistance to penicillin was 15%; to erythromycin, 15%; to chloramphenicol, 31%; and to cefotaxime, 23%. The penicillin-resistance rate among blood and cerebrospinal fluid pneumococcal isolates was 17% during 1993-1994. Drug-resistant S. pneumoniae is now a recognized cause of pleural empyemas in children.