This is a retrospective study of 31 cases of acute septic arthritis of the hip in children treated at Chang Gung Memorial Hospital from 1983 to 1989. The average follow-up period was 35 months. Among them, there were 18 males (58%) and 13 females (42%). None were involved bilaterally. Fifteen cases (48%) were below 5 years of age. All cases met the diagnostic criteria including bacteriological results, clinical and radiographic changes. Limited range of motion, fever, and tenderness were the most common symptoms and signs. More than half of the patients (52%) had a leukocyte count of over 15,000/cmm. The erythrocyte sedimentation rate was elevated in 30 cases (97%). Pathogens had been isolated from blood, arthrocentesis fluid, or surgical specimens in 26 cases (84%). Staphylococcus aureus was the most common causative organism (58%). Twenty-seven cases (87%) underwent emergency arthrotomy and debridement. Five (19%) of them received unsatisfactory results. A delay in definite treatment, very young infants, and the association with osteomyelitis of the adjacent bone were the important factors associated with poor prognosis. Four cases (13%) who received only medical treatment showed satisfactory results. Early diagnosis and significant response to antibiotics contributed to this favorable outcome.