The effect of parenteral nutrition (PN), combined with corticosteroid therapy, on body composition was evaluated in 22 pediatric patients with active and complicated inflammatory bowel disease (IBD). The patients were divided into two groups according to the duration of PN. Group A consisted of 14 patients who received PN for an average of 43 days (short term) whereas eight patients received PN for an average of 104 days (long term); group B. Nutritional assessments were performed before and following the PN periods. In addition, a follow-up assessment was performed 50 days after the cessation of PN for group A. Serial evaluations included; weight, height, disease activity score, arm anthropometry, subscapular skinfold (SSSF) thickness, 24-hr urinary creatinine, and computed tomography (CT) scan of the thigh. Following PN with a glucose-fat mixture used as a nonprotein energy source, there were significant (p less than 0.05) increases in weight, SSSF, and muscle mass (MM) in both groups. Disease activity declined in both groups and height increased in group B and at the follow-up assessment for group A. Considering extremity composition, both groups exhibited increases in midarm muscle area, midarm fat area, thigh muscle area, and thigh fat area. However, a differential distribution of incremental change was observed depending on the duration of PN. Fat deposition predominated in both the upper and lower extremities for group A. Group B patients, however, although showing a predominance of fat accumulation in the upper extremities, gained muscle and fat components equally in the lower extremities.(ABSTRACT TRUNCATED AT 250 WORDS)