The routine addition of tannic acid to barium enema preparations to enhance colonic evacuation and mucosal detail was suggested by Hamilton in 1946 (6). According to Weber, however, tannic acid was used as early as 1930 by some radiologists (6). Following Hamilton's report, it gained widespread acceptance and was employed by a large number of radiologists in this country. In recent years Clysodrast, a bowel evacuant in which tannic acid is the active agent, has been introduced. On March 21, 1964, the Food and Drug Administration banned the use of tannic acid in barium enemas as well as in pre-enema preparations, effective in sixty days (4). This ban followed the publication of two papers (10, 11), reporting a total of 8 cases of hepatic necrosis and death presumed secondary to tannic acid in the preparation and∕or the performance of barium enemas. Since this decision so profoundly affects many radiologists, it is believed worthwhile to review and evaluate the importance of tannic acid or similar compounds...