Septic arthritis affects weight-bearing joints in three fourths of cases. When the disease occurs in infancy, joint dysfunction may not be apparent until many months later. We located 49 children who had had 50 episodes of septic arthritis from 1 1/2 to 12 years earlier (mean, 4.3 years). Thirteen patients (27%) had sequelae, and in eight (16%), there was impairment of ambulation. Residual damage was more common with hip and ankle involvement than with knee joint disease. Sequelae were equally common after Haemophilus influenzae and Staphylococcus aureus infection. Evaluation at the time of hosiptal discharge correctly identified only four of the 13 children with sequelae, and four others who were normal at follow-up had been thought to have permanent damage at discharge. Children with sequelae tended to have been sick longer before diagnosis, and drainage of pus was delayed.