The aim of this study was to compare the effects of a genetically engineered glucagon (geG) and hyoscine N-butylbromide (HBB) on the quality of double-contrast barium meal (DCBM) study. Two hundred sixty-four patients scheduled for DCBM were randomized to receive intravenously geG 0.25 mg (geG-25), or geG 0.5 mg (geG-50), or HBB 20 mg as hypotonic agent. The evaluation concerned: duration of isolated visualization of the stomach (A); gastric mucosal coating (B); visualization of areae gastricae (C); quality of duodenal cap (D) and loop (E) study; delay, if any, of duodenal study (F). Global significant differences (P from 0.0183 to < 0.0001) were found for A, C, D, and F. GeG-50 allowed the longest isolated gastric visualization (P < 0.0001); geG-25 allowed more extensive visualization of areae gastricae than HBB (P = 0.0006); HBB allowed a better study of duodenal cap (P = 0.0052) and loop (P = 0.0190) than geG-25; geG-50 prolonged the examination time (P < 0.01). No adverse effect was observed with geG within 1 h after DCBM. In conclusion, geG can be safely used as a hypotonic agent in DCBM. When DCBM is focused on the stomach, 0.25 mg of geG is the optimal choice; if DCBM is focused on the duodenum, 0.5 mg of geG (with a prolonged examination time) or 20 mg of HBB (with a less effective study of the stomach) should be used.