In this morphologic experimental study in the rabbit disturbances in the microcirculation at the site of colonic anastomoses were found in all suture techniques employed. They are caused by resection, intraoperative traumatization, the suture technique, and, secondarily, by abscess formation on the anastomosis. The suture-induced disturbances of the microcirculation lead to necroses of the mucosa, partial and complete necroses of the inverted cuff, and transmural necroses with destruction of the sero-serous contact zone. For the pathogenesis of anastomotic dehiscence only transmural and extensive complete necroses of the anastomotic bulge, including the serosal contact, are important. They result in transmural abscess formations which correspond to microscopic small secondary anastomotic leakages.