Transanal endoscopic microsurgery (TEM) was first used on a regular basis in the United States in 1990. Because there is a sole source of instrumentation, the surgeons who use this equipment are known to us. Thus, this earliest registry is a compilation of data based on most patients who underwent TEM in the United States from 1990 to 1994.One hundred fifty-three cases were voluntarily registered by six surgeons. Pathology included 54 carcinomas, 82 adenomas, and 17 other entities. Most resections were full thickness. Fifty percent of cases were out of reach of standard instruments. Complication rate, hospital stay, and blood loss were recorded. Technical difficulties at time of surgery (9 percent), early complications (15 percent), and late complications (5 percent) have been tabulated.Recurrence rates for carcinoma were 10 percent for T1, 40 percent for T2, and 66 percent for T3 stages. Failures were treated by abdominoperineal resection or low anterior resection. Adenomas recurred in 11 percent, but these recurrences were small and easily treatable.TEM has a low complication rate. By carefully selecting small, superficial cancers and adenomas, TEM results in superior outcome over other approaches to the mid and upper rectum.