Intrarenal infusion of forskolin (0.2 microgram/kg/min) in anesthetized dogs increased renal blood flow (RBF) and glomerular filtration rate (GFR) to the same degree but did not change the mean arterial pressure or heart rate. Forskolin also increased urine flow and urinary sodium excretion. The proportional increases in RBF and GFR may result from a preferential action of forskolin to dilate the afferent arteriole.