Abstract— The effect and mechanism of action of calcitonin gene‐ related peptide (CGRP) have been investigated on the mouse distal colon. CGRP caused a concentration‐dependent relaxation which was not blocked by classical pharmacological antagonists. The response pattern was characterized by a relatively rapid onset and long sustained duration. The results suggest that CGRP itself may contribute to regulating the muscular tone of the mouse colon. 1990 Royal Pharmaceutical Society of Great Britain