The responses to angiotensinogen, angiotensinogen-(1-14) (tetradecapeptide, TDP), angiotensin I, and angiotensin II and the effect of the renin inhibitor, CH-66, the angiotensin-converting enzyme (ACE) inhibitor, perindopril, and the receptor antagonist, saralasin, were investigated in isolated femoral resistance arteries of the rat. The response to angiotensinogen in the presence of kallikrein was also investigated. Angiotensin I and TDP elicited a contraction which was not reduced by CH-66 but was inhibited by perindopril and saralasin. The response to angiotensinogen was small and not blocked by saralasin but the response to angiotensinogen that was mixed with renin for a few seconds was saralasin-sensitive and perindopril and CH-66 showed a tendency to block this response. The response to angiotensinogen was enhanced in the presence of kallikrein. These results suggest (1) the presence of a partial renin-angiotensin system (RAS) in this preparation, (2) that TDP is not converted via renin while both angiotensin I and TDP are converted through ACE in this preparation and (3) that the responses to angiotensinogen and TDP are different.