Ninety-three patients for whom a colorectal operation was planned had their bowel prepared mechanically by orthograde irrigation. The tube was sited in the duodenum via the pylorus under X-ray and TV control. The procedure was discontinued in 2 patients (2%), 15 patients (16%) experienced nausea and vomiting, while 76 patients (82%) experienced no discomfort. The mean duration of the irrigation was 216 min (90-476 min) and the mean volume of fluid used 10.21 (5.0 -15.0 1). There were no significant differences between pre-irrigation and post-irrigation blood chemistry. Twenty-three patients developed postoperative abdominal wound sepsis (26.7%), 4 (4.7%) had an intraabdominal abscess; 9 out of 12 patients (75%) had perineal wound sepsis. Escherichia coli and Bacteroides were the dominant species cultured from colorectal mucosa during operation as well as from infected abdominal and perineal wounds. Although the irrigation technique seems to clean the bowel to a degree not previously seen, this in itself is no guarantee of avoiding post-operative wound sepsis after colorectal operations.