The influence of captopril and ritanserin (5-HT2 receptor antagonist) on the serotonin-induced contraction of isolated tail artery of two-kidney, one clip hypertensive (2K, 1C-RHR) and normotensive rats was studied. Captopril, administrated in a single dose of 100 mg/kg, po or in a dose of 30 mg/kg/day, po for one week, diminished the systolic blood pressure in both groups of rats. Ritanserin (0.01 mg/kg/day, sc for one week) administrated alone or in combination with captopril (30 mg/kg/day) evoked such effect only in 2K, 1C-RHR. The reactivity of rat tail artery isolated from 2K, 1C-RHR to serotonin was significantly higher than that obtained from normotensive ones. Captopril given in a single dose or chronically did not change the serotonin-induced contraction of rat tail artery in normotensive rats. The attenuation of serotonin contractile effect was registered in hypertensive rats pre-treated with captopril. Administration ritanserin with or without captopril also inhibited the response to serotonin in both groups. The stronger effect was observed after administration of ritanserin with captopril in 2K, 1C-RHR than in control group. Our results indicate, that in 2K, 1C-RHR the reactivity of rat tail arteries to serotonin is enhanced and this effect can be reduced by chronic captopril administration.