Surgical alteration of rabbit oviducts was employed to investigate the mechanisms of ovum transport. Resection of a 5- to 10-mm segment of midampulla was followed by microsurgical end-to-end anastomosis. One to two months later, direct observations were made, in situ, of ampullary egg transport. Stained cumulus masses were transported normally to the site of anastomosis: two-thirds of those studied were delayed at that point for an average of 2 1/2 minutes. Normal transport then resumed and continued to the ampullo-isthmic junction. In all but one instance, blockage of muscular activity with isoproterenol prevented transport beyond the anastomosis site, demonstrating the presence of an obstacle to ciliary transport. These studies reveal an important facilitative role for muscle in improving the reliability of ampullary egg transport. Considering species differences in egg transport mechanisms, it is suggested that ampullary-ampullary anastomosis in women might have a poor prognosis for re-establishing fertility.