In vitro labelling of neuropeptide Y binding sites with 125I-NPY was performed in rabbit kidney sections. Autoradiographic and histochemical techniques localised these binding sites to the proximal convoluted tubules and the vascular smooth muscle. In comparison, 125I-NPY binding was absent from the rat, guinea pig and human kidney. Possible physiological roles for the putative NPY receptors in rabbit renal function are discussed.