To examine the effect of isoflurane on systemic hemodynamics and renal blood flow, the author measured mean arterial pressure, cardiac output, central venous pressure, renal blood flow and plasma renin activity by administration of 1 MAC and 2 MAC isoflurane with 50% nitrous oxide to dogs. From the above results total peripheral resistance and renal vascular resistance were calculated. The results are the following: 1) With an increase in isoflurane MAC, mean arterial pressure and cardiac output were decreased. 2) Total peripheral resistance did not differ between the control and 1 MAC isoflurane but decreased with 2 MAC isoflurane. 3) With an increase in isoflurane MAC, renal blood flow and renal vascular resistance were decreased but the decrease in renal blood flow was comparatively less than the decreases in mean arterial pressure and cardiac output. 4) Plasma renin activity was increased with an increase in isoflurane MAC. It is concluded that isoflurane decreases renal blood flow by decreasing mean arterial pressure and cardiac output in dogs, but it is strongly suggested that renal blood flow does not decrease more markedly than expected from the decreases in mean arterial pressure and cardiac output by direct dilation of renal vasculature and/or autoregulation.