Secoverine hydrochloride is a new synthetic tertiary amine with selective muscarine blocking effect. Its tendency to produce parasympathetic side effects has been claimed to be almost 100 times less than atropine. We studied the role of secoverine on meal-induced colon motor and myoelectrical activity in 12 healthy volunteers. lntraluminal pressure changes, slow wave activity, and spike frequency of the sigmoid colon as well as a pneumogram, blood pressure, and electrocardiogram were monitored. Fifteen minutes after ingestion of a 1000-kcal meal, subjects received 4 mg secoverine or the same volume of normal saline in separate sessions and recording continued for another 90 minutes. Ingestion of the meal increased colon motor and spike activities; however, these parameters were not influenced by secoverine. Drug treatment did not change the proportion of slow wave activity and did not affect pulse rate, blood pressure, respiration rate, or electrocardiogram in a significant fashion. In conclusion, intravenous injection of 4 mg secoverine had no effect on meal-stimulated colon motor and myoelectrical activity. Whether this medication at a different dose regimen has therapeutic value remains to be seen. However, this dose of secoverine was well tolerated by the subjects.