Medical records of 111 children discharged with the diagnosis of septic arthritis from 1973 through 1985 were examined; 122 infected joints were identified. Bacteria were isolated from joint fluid of 75 patients and from blood, cerebrospinal fluid, cervix, bone, or wounds of 16. No agent was isolated from 20 patients, of whom eight had been pretreated with antibiotics. The knee and hip were most often affected overall (73/122), although the ankle was as frequently involved with Haemophilus influenzae type b (6/20). Eighty patients' condition resolved with no sequelae; 18 were unavailable for follow-up. Of the 13 patients with permanent sequelae, ten had had hip joint infections. Although Staphylococcus aureus was isolated from patients of all ages, H influenzae type b was the most frequent pathogen in children 6 through 59 months of age.