Summary In the conscious, trained dog we have noted an increase in apparent renin secretion following renal artery constriction and reduction of renal arterial pressure, with little or no change in renal blood flow, and without significant change in distribution of cortical blood flow. Within 2-5 days, however, basal renin secretion rates declined toward normal despite maintained renal arterial hypotension; body fluid volume was increased. A highly significant correlation between systemic blood pressure and body wt was noted. With release of the cuff, a natriuresis and diuresis was observed, with a return of body weight and hematocrit to normal within the first 24-48 hr. However, despite the decrease in body fluid, and the decrease in renin secretion and PRA, blood pressure returned to control level more slowly, suggesting a resetting of the baroreceptor reflex.