It has been recently reported that valine, which was one of the branched chain amino acids, enhanced liver regeneration after a hepatectomy in rats. The aim of this study is to investigate the effect of enteral valine supplementation on the intestinal adaptation of short bowel syndrome using a rat model. Seven-week-old male Lewis rats underwent a 90% small bowel resection. The rats were randomly divided into two groups; Group V (valine-rich diet which contains valine, five times as the normal amount of valine as that found in standard rat chow) and Group S (standard rat chow), according to the diet each group received. The rats were killed and evaluated at the operative day, and postoperative days (POD) 7, 14, 30, and 60, respectively. The parameters of estimation were body weight (BW), a blood amino acids analysis, a urine organic acids analysis and a morphological examination of the residual small intestines. The BW and the intestinal wet weight, jejunal crypt depth and proliferating cell nuclear antigen positive cells in Group V at POD 7 were significantly higher than in Group S, while those in the Group V at POD 30 and 60 were smaller than in Group S. The urine methylmalonic acid (MMA) level in Group V at POD 30 and 60 was much higher than in Group S. The valine-rich diet was thus found to enhance intestinal regeneration after a small bowel resection in the acute phase. However, the long-term valine-rich diet supplementation was found to disturb the intestinal adaptation, which might be caused by the high production of MMA due to the valine-rich diet. This is the first report in which valine was used as a promoter of intestinal adaptation.