Septic arthritis of the hip must be managed promptly to avoid the serious complications associated with the condition. In the case reported here, the diagnosis was delayed and was complicated by a slipped capital femoral epiphysis. The patient, an adolescent boy previously in good health, presented with a 2-week history of hip pain and systemic illness. Septic arthritis was diagnosed and was managed by incision and drainage and antibiotic therapy. Two weeks later he presented with a subcutaneous abscess and a slipped capital femoral epiphysis, which was pinned in situ. There was a 2.5-cm leg-length discrepancy. Avascular necrosis of the femoral head subsequently developed leaving the boy with a permanent disability.