Acute purulent arthritis (APA) in children is a rare disease. A series comprising 25 children with APA seen in 1960-79 was analysed with regard to clinical problems of diagnosis and treatment. The sex ratio of boys to girls was 2.5:1. The knee joint was most commonly affected (76% of the cases). The other joints affected were the hip (16%), ankle (4%), and elbow (4%), 56% of the patients were 1-2 yr old at the onset of the disease. A bacterial etiology was established in 44% of cases; a positive culture in 36%. Staphylococcus aureus, Haemophilus influenzae, streptococci, and pneumococci were isolated. All but 2 patients received antimicrobial therapy; the duration of therapy averaged 35 days. Seven patients were treated operatively. The usual procedure was arthrotomy, and closed irrigation was performed in 2 cases only. The end result was good in all cases. There were no fatalities.