This study evaluates the direct effects of verapamil and furosemide infused into the unilateral renal artery on renal function and the renin secretion rate in renal vein-catheterized rabbits. Catheterization did not alter the renal function parameters of the kidney. Verapamil and furosemide increased renal blood flow, urine flow, and urinary sodium, potassium and chloride excretions confined to the infused kidney. Verapamil increased the glomerular filtration rate and free water clearance. The renin secretion rate was increased by furosemide but not by verapamil. The present study shows that the technique is applicable to renal function studies in which unilateral renal arterial infusion of the agents studied is required. The contralateral kidney can be a reliable control for the infused kidney. It also provides a useful technique for the study of renin release in rabbits.