In the dog, alpha₁ adrenoceptors have been identified in the aorta, femoral mesenteric, and renal arteries. The concentration of alpha receptors may be regulated by hormones such as estrogen and progesterone and by drugs such as epinephrine. To assess whether sympathetic denervation, which is known to decrease norepinephrine output, might change the population of alpha, receptors in vascular smooth muscle, the femoral artery alpha, receptor population was examined 2 weeks after unilateral lumbar sympathectomy [³H] Prazosin radioligand receptor assay analysis was used to measure the alpha, receptor populations. No statistical difference for dissociation constant and receptor density values between sympathectomy and nonsympathectomy femoral artery samples could be detected.