Specific high-affinity (K d = 3.4 nM) binding sites for 1 2 5 I-labelled angiotensin I (I 1 2 5 I]Ang I) were identified on an epithelial cell line (IEC-18) derived from the rat small intestine. The sites, which also have high affinity for Ang II, are insensitive to both AT 1 - and AT 2 -specific angiotensin receptor antagonists. The rank order of potency with which various angiotensin peptides inhibited [ 1 2 5 I]Ang I binding to the cells (Ang I ≥ Ang II > Ang(1-7) > [Sar 1 ,Ile 8 ]-Ang II > Ang(3-8) > Ang III) also distinguishes these sites from AT 1 and AT 2 angiotensin receptors.