Conventional surgical techniques play an important role in rectal cancer. Dehiscence of the anastomosis after low anterior resection of the rectum is a serious complication. The incidence of dehiscences can be reduced when known principles of preoperative care are respected but in particular by correct surgical technique. In 92 patients operated for rectal cancer at First Surgical Clinic of Charles University we had six patients (6.5%) with dehiscences of anastomosis. The serious character of this surgical complication can be reduced by a primary derivative stomy. Authors recommend implementing a preventive ileostomy in low resection of the rectum in high-risk patients.