AIM: To investigate the effect of donor splenocyte infusion combined with cyclosporine A (CsA) on rejection of rat small bowel transplantation (SBT).METHODS: Male Sprague-Dawley (SD) rats and female Wistar rats weighing 230-270 g were used as donors and recipients respectively in the study. Heterotopic small bowel transplantation was performed. The rats were divided into three groups: group one receiving allotransplantation (SD→Wistar), group two receiving allotransplantation (SD→Wistar) + donor splenocyte infusion, group three receiving allotransplantation (SD →Wistar) + donor splenocyte infusion + CsA followed by CsA 10 mg/kg per day after transplantation, in which recipient Wistar rats were injected with 2 ×108 SD splenocytes 28 d before transplantation, and treated with CsA after transplantation. Finally, the specific DNA fragment of donor Y chromosome was detected in recipient peripheral blood and skin by PCR. The survival time after small bowel transplantation was observed.Gross and histopathological examinations were performed.RESULTS: The survival time after small bowel transplantation was 7.1 ± 1.2 d in group 1, 18.4 ± 3.6 d in group 2 and 31.5 ± 3.1 d in group 3. The survival time was significant longer (P ＜ 0.01) in group 3 than in groups 1 and 2. The gross and histopathological examination showed that the rejection degree in group 3was lower than that in groups 1 and 2.CONCLUSION: Donor splenocyte infusion combined with CsA decreases remarkably the rejection and prolongs the survival time after rat small bowel transplantation.