In this study, the effects of intraperitoneal 5-fluorouracil (5-FU), cisplatinum (Cis), adriamycin (Adr), and methotrexate (MTX) administration on rat intestinal anastomosis were compared. Cis and MTX led to significant weight loss in the first 5 days compared with the control group. Within 14 days all rats except the MTX group nearly reached their preoperative weight. No remarkable weight loss or systemic toxicity was observed among the 5-FU and Adr groups. The anastomosis bursting pressure (ABP) at 1 week was significantly lower than that of the control group (P < 0.01 and P < 0.005, respectively). On day 14 the anastomosis bursting pressure in the Cis group was similar to that of the control group but was significantly lower in the MTX group (P < 0.002). Histopathologically, MTX avoided the development of a mucosal layer at the anastomosis site and led to ulcer formation in some of the rats. The ABPs at 7 and 14 days were similar to those in the control group. Neither of the agents had any significant mechanical or histopathologic adverse effects on anastomosis. According to the results of our study, MTX impaired the healing of the anastomosis, and we thus conclude that the intraperitoneal administration of this agent is not safe. On the other hand, Cis showed a detrimental effect on the anastomosis, particularly in the early phase, but this effect disappeared in the late phase. Cis thus should not be administered in the early postoperative phase. As a result, 5-FU and Adr were found to be the safest agents as they did not delay wound healing and did not reduce the anastomotic strength.