Objective To assess the value of primary resection and anastomosis without intraoperative irrigation in the patients with obstructive left colonic cancer. Method Between January 2000 and January 2008, 93patients underwent primary resection and anastomosis for colonic cancers were analyzed retrospectively. Primary resection and anastomosis without intraoperative colonic irrigation (decompression by manual defecation) was performed in 43 patients with obstructive left colonic caner and traditional left-sided colectomy in 50 cases without obstruction. Both groups of patients were comparable in terms of gender, nutritional status, underlaying disease, tumor location and stage, etc ( P = 0.83,0.13,0.29,0.51,0.38). The average age of the patients with colonic obstruction was significant older than that of the cases without obstruction (61.2 ± 8.6 vs. 58.1 ±7.8, P =0.010).The operative results were compared between patients with obstructive colonic cancer and cases without obstruction.Results The mean hospital stay of the primary anastomosis group and traditional left-sided colectomy group were (16.6±7.8) d and (12.4±5.4) d respectively, and the former was significant longer than the latter (P =0.002). The costs of hospitalization in the two groups were (50192.8 ± 39727.4) RMB and (46489.3 ±29543.1)RMB respectively (P = 0.04) . The morbidity and mortality in the two groups were 25.6% (11/43) vs. 18%(9/50) (P =0.375) and 2.3% (1/43) vs. 2.0% (1/50) (P =0.714) respectively, and there were no significant difference between the two groups. Conclusions Primary resection and anastomosis without intraoperative colonic irrigation (decompression by manual defecation) compares favorably with traditional left-sided colectomy in safety and efficiency for left colonic cancer with obstruction.