There has been recent evidence linking bradykinin (BK) receptors with inflammation. This study has investigated the involvement of BK receptors in two models of persistent inflammatory hyperalgesia in rats. In a Freund's adjuvant-induced hyperalgesia model and an ultraviolet (UV)-induced hyperalgesia model in rats the specific B2 antagonist, D-Arg[Hyp3, Thi5, D-Tic7, Oic8]-BK (HOE 140), was either ineffective or weakly active in reversing hyperalgesia. The specific B1 antagonist, des-Arg9, [Leu8]-BK, was effective in reversing or preventing the development of hyperalgesia in both Freund's adjuvant-induced hyperalgesia and UV-induced hyperalgesia. The B1 agonist, des-Arg9-BK, produced a small exacerbation of hyperalgesia in both models. Data suggest that in persistent inflammatory conditions in the rat bradykinin B1 receptors are involved in the accompanying hyperalgesia.