A range of bradykinin (BK) analogues was assessed for their ability to antagonise the action of BK on rabbit jugular vein, a B₂-receptor containing tissue, and compared with their action against BK-induced increases in skin vascular permeability in the rabbit and rat. The results demonstrate that modification of the BK (nonapeptide) structure by the insertion of certain d-amino acids in positions 5, 7 and 8 in addition to elongation of the amino terminal resulted in compounds with potent antagonistic action against BK on rabbit jugular vein and rabbit skin vascular permeability. The same BK analogues did not antagonise the action of BK on rat skin vascular permeability. It is concluded that the kinin receptor mediating an increase in vascular permeability in the rabbit is the same as that mediating contraction of the rabbit jugular vein in vitro, that is the B₂-type. The kinin receptor mediating an increase in skin vascular permeability in the rat is difficult to classify but does not appear to be of the B₂ type.