OBJECTIVE To document the radiologic abnormalities in patients with systemic onset juvenile rheumatoid arthritis (SOJRA) including abnormalities occurring early in the course of disease. METHODS A retrospective review of the charts and radiographs of 42 consecutive children with SOJRA was carried out. Radiographs were reviewed by a single experienced radiologist with no knowledge of the clinical course of the patients. RESULTS Soft tissue swelling and osteoporosis were the most common radiologic abnormalities (34/42; 81%). Cartilage loss and/or bone erosions were also common, occurring in 50% of patients. Erosions occurred within 2 years of disease onset in 11/36 (31%). Subchondral irregularity and sclerosis within 2 years of disease onset preceded erosions in 11 patients with serial radiographs. Severe radiologic abnormalities included joint ankylosis (8/42; 19%), subluxation (9/42; 21%), and protrusio acetabuli (4/42; 10%). Joint ankylosis occurred most commonly between 3 and 5 years after disease onset and subluxation between 2 and 6 years. CONCLUSIONS A subgroup of children with SOJRA develops early destructive radiologic changes whose severity is comparable to those of children with rheumatoid factor positive polyarticular JRA. Early subchondral changes may be predictive of subsequent erosive disease in SOJRA and require prospective study using newer imaging techniques.