Laparoscopy-assisted colectomy is technically feasible, but objective evidence of its benefits remains scarce. This study was done to evaluate the outcomes and operative stress of laparoscopy-assisted colectomy versus the traditional open method in the management of sigmoid complex polyps that cannot be safely or adequately removed by colonofibroscopy. Between January 1997 and December 1999, a total of 42 patients were equally randomized to the laparoscopy group and the laparotomy group by the blocked randomization method. Three patients randomized to the laparoscopy group did not complete the trial; therefore 18 patients treated by laparoscopy-assisted sigmoidectomy and the other 21 treated by the open method were prospectively evaluated. These two groups of patients were well matched in age, gender, symptoms, tumor location, localization method, tumor size, morphology, histopathology, and the accuracy of the clinical diagnosis. Two standardized surgical strategies, the lateral-to-medial and medial-to-lateral dissection sequences, were performed in 14 and 4 patients of the laparoscopy group, respectively, according to whether their tumors were located above or below 20 cm above the anal verge. After evaluating the surgical outcomes, we found that the laparoscopy group was significantly better than the laparotomy group in regard to parameters that included severity of postoperative pain, wound size, postoperative complication rate, and the duration of postoperative ileus, hospitalization, and disability. There was no significant difference in the operating times for these two groups. However, the costs of the laparoscopy group were significantly higher. To evaluate the surgical stress, we measured the serum C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR), total lymphocyte count, and CD4+/CD8+ ratio 24 hours before and after surgery. We found that the postoperative serum CRP level and the ESR were significantly less elevated and the total lymphocyte counts and CD4+/CD8+ ratio were significantly less depressed in the laparoscopy group than in the laparotomy group. We thus concluded that laparoscopy-assisted sigmoidectomy can be safely performed with shorter convalescence and less operative stress but at a higher cost. We strongly recommended the use of this technique in the management of sigmoid complex polyps if the patient's economic status permits.