Rectal cancer surgery is difficult due to the rectum's relatively inaccessible pelvic position and its direct relation to many vital structures. The surgeon is challenged to restore intestinal continuity while working in a confined space. Despite the importance of these issues, the embryology and surgical anatomy of the rectum have been poorly understood. In recent years, cadaver dissections and operative resection under direct vision have provided a clearer picture of the structure of the rectum and mesorectum, their innervation, blood supply, and surrounding structures. New imaging techniques will shed further light on the anatomy of these structures and their anatomic variations.