The aim of this study was to investigate the correlation between the expression of transforming growth factor-beta 1 (TGF-beta 1) in the mucosal tissue of rat small intestine and the apoptosis of epithelial cells in the small intestine in a cold-restraint stress state. Immunohistochemistry was used to detect the expression of TGF-beta 1. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) and DNA agarose gel electrophoresis were used to detect apoptosis. After 8 and 12 h of cold-restraint stress, the positive expression rate of TGF-beta 1 in the rat small intestine epithelial tissue was 59.09 and 54.16%, respectively. The apoptotic index (AI) of the rat small intestine epithelial cells was 25.69 +/- 8.09 and 19.65 +/- 6.61%, respectively. The positive expression rate of TGF-beta 1 in the epithelial tissue of the rat small intestine was positively correlated with the AI of the epithelial cells (r=0.980, P<0.05). The epithelial cells of the rat small intestine exhibited apoptosis under cold-restraint stress. TGF-beta 1 is one of the key factors that induces apoptosis of the epithelial cells of the rat small intestine.