From 1979 to 1985, 18 patients who were found to have proximal tubal obstruction by hysterosalpingography and laparoscopic chromopertubation underwent resection of the obstructed tubal segment and reimplantation or microanastomosis. Resected tubal segments were studied histologically, and in 11 of the 18 cases no tubal occlusion could be demonstrated. A variety of histologic abnormalities were noted, however, including six cases in which the tubal lumen contained an amorphous material of unknown etiology, often appearing to form a cast of the tube. Such "plugs," which the authors believe to be previously unreported, have no clearly established clinical significance at present. However, if they cause tubal occlusion, this would explain several previously published findings, and would also have implications for therapy.