Abdominal trauma, such as surgery and peritonitis, leads to inhibition of intestinal motility, partly mediated by alpha- and beta-adrenoceptors. To investigate the effect of nonselective beta-blockade on adynamic ileus, propranolol was compared with placebo in the postoperative course after elective colonic surgery in a double-blind randomized study. Ten patients received 4 mg propranolol intravenously twice daily, and ten received 10 mg intravenously twice daily. Nineteen patients received placebo. The time to first passage of stool was 110 +/- 9 h in the placebo group and 82 +/- 11 h in the 4-mg propranolol group. In the 10-mg propranolol group, the time was 79 +/- 8 h. The difference between the placebo-treated group and the propranolol-treated groups was significant (p less than 0.01). The effect of propranolol was most marked in older patients and after surgery on the distal colon. In patients older than 60 years the time to first stool in the placebo group was 127 +/- 13 h (n = 8), compared with 73 +/- 8 h (n = 11) in the propranolol group (p less than 0.01). In patients who had undergone surgery on the distal colon the time to first stool was 125 +/- 13 h (n = 8) in the placebo group and 76 +/- 8 h (n = 11) for propranolol (p less than 0.01). Adverse effects on the respiratory or cardiovascular system were not seen during medication. It is concluded that propranolol shortens the period of adynamic ileus after colonic surgery.