The aim of this study was to determine the kinin responses on human umbilical artery (HUA) and to characterise the kinin receptors present on this tissue. The HUA was found to constrict in response to both the B 2 receptor agonist, bradykinin (BK), and the B 1 receptor agonist, des-Arg 9 -BK. The presence of indomethacin (2·79 µM) was found to have no significant effect on the responses to BK and des-Arg 9 -BK. The presence of the B 2 receptor antagonist, HOE-140 (+2·79 µM indomethacin), resulted in a concentration-related rightward displacement of the concentration-effect curves to BK. The antagonism of the constrictor responses to BK by HOE-140 was found to be competitive (pA 2 =7·5). The responses to BK were not significantly affected by the B 1 receptor antagonist des-Arg 9 (leu 8 )BK. The presence of des-Arg 9 (leu 8 )BK (+2·79 µM indomethacin) resulted in a concentrationrelated rightward displacement of the concentration-effect curve to des-Arg 9 -BK. The antagonism of the response to des-Arg 9 -BK by des-Arg 9 (leu 8 )BK was found to be competitive (pA 2 =5·9). The responses to des-Arg 9 -BK were not significantly affected by HOE-140. The results of the present study suggest that the products of the cyclooxygenase pathway are not involved in the kinin constrictor response on HUA and indicate the presence of B 1 and B 2 receptors on this tissue.