Surgery is the mainstay of therapy for colon and rectal cancer. Over the past several decades, there have been important advances both in the understanding of the biology of colon and rectal cancer and in the preoperative and operative techniques for treating this disease. Although it appears in some studies that we have made a difference in the survival rates in the treatment of colon and rectal cancer, in actual fact, this phenomenon may only be secondary to better staging and, therefore, a greater ability to prognosticate a particular patient's chance of cure. What has been learned in the past 20 to 30 years is that most colon and rectal carcinomas start as polyps of the colon and rectum. Most often, polyps are sporadic, but there are certain high-risk groups that produce polyps and, consequently, colon and rectal cancer at a much higher rate. The goal of a practicing physician is to identify these high-risk individuals and to recommend frequent screenings so as to intervene before a polyp has had a chance to become a deeply invasive cancer. These high-risk groups are best typified by familial adenomatous polyposis, which if left untreated will, in 100% of cases, lead to the death of a patient from colon or rectal cancer. Other diseases that lead to an increase in colon and rectal cancer but may not go through the usual adenoma-to-carcinoma sequence include inflammatory bowel disease such as Crohn's colitis and ulcerative colitis. Most patients with colorectal carcinoma are asymptomatic at the time of diagnosis. This phenomenon has led to efforts to screen the general population for polyps and for cancer. Screening techniques such as the detection of occult blood in the stool and endoscopic procedures are currently the most popular. It is unclear at this time exactly what the efficacy of these techniques is in improving the survival of the general population from colorectal carcinoma. The surgical techniques to remove colon and rectal carcinomas have recently expanded to include a more aggressive local excision policy for small tumors of the rectum and the application of laparoscopic techniques, new stapling techniques, and new anastomosing techniques for tumors of the colon and rectum. These techniques have become possible in part through advances in surgical instrumentation and also in part from our increasing understanding of the biology of the disease. Both have allowed for more creative approaches to diagnosing and treating colon and rectal cancer.(ABSTRACT TRUNCATED AT 400 WORDS)