1. Binding sites for 125I-labeled endothelin (ET) isopeptides ET-1, ET-2 and ET-3 were visualized by autoradiography in the kidneys of man, baboon, rhesus monkey, tree shrew, pig and rat. 2. Highest levels of binding for the three isoforms were observed in the glomeruli, cortical and medullary vessels of baboon, rhesus monkey, pig and rat, whereas there was no noticeable labeling of glomeruli in human and tree shrew kidneys. 3. The enrichment of binding sites depended on the species and peptide investigated, suggesting different affinities and/or densities of a heterogenous population of renal ET receptors.