The aim of this study was to evaluate the effects of the prolonged duration of total parenteral nutrition (TPN) on the clinical, laboratory, and nutritional parameters and short-term outcome in acute attacks of ulcerative colitis and Crohn's colitis, and the difference in the response to TPN between the two diseases. Twenty-two patients with severely and moderately active ulcerative colitis (8 severe and 14 moderate) and 12 patients with Crohn's colitis were analyzed retrospectively. Eleven of 22 patients with ulcerative colitis were treated with TPN and corticosteroids (TPN group). The remaining 11 patients were treated with corticosteroids alone and hospital meals (oral diet group). Both groups were matched regarding disease severity at pretreatment. The clinical characteristics, and the initial and total dosages of corticosteroids for 3 weeks were similar between the two groups. The authors compared the changes in the clinical, inflammatory, and nutritional parameters and short-term outcome between the TPN and the oral diet groups with ulcerative colitis. The same evaluations were also made for 12 patients with Crohn's colitis who received TPN (CD group). The TPN group did not show any significant improvement in the clinical parameter, inflammatory signs, or nutritional state compared with the oral diet group with ulcerative colitis. The remission rate after 3 weeks of therapy and a colectomy rate also showed no significant difference between the two groups. In contrast, TPN resulted in a disappearance of clinical symptoms and an improvement in both the inflammatory and nutritional parameters in the CD group. Only one of the 12 patients with Crohn's colitis underwent colectomy. TPN induced no additional benefit in corticosteroid therapy in an acute attack of ulcerative colitis. In contrast, TPN may have primary effects on Crohn's colitis.