Six dogs were examined by means of single- and double-contrast barium enemas, and colonic pressures and diameters were recorded at five intervals while the volume of the contrast medium was increased. Examinations were performed with and without administration of glucagon. Changes in colonic pressure and diameter were similar for the two techniques in 77% of the studies with and in 65% of the studies without administration of glucagon. Neither technique produced significantly different pressure or diameter changes with glucagon as compared to without it. Limitations in the experimental technique must be considered before extending results to human subjects.