The time course of the paw oedema induced by the subplantar injection of carrageenan was studied in rats treated neonatally with capsaicin and in their vehicle-treated controls. In the capsaicin-treated rats, which show a permanent deficit of unmyelinated primary sensory neurones, carrageenan produced an oedema which was larger and lasted longer than in the vehicle-treated rats. Pretreatment with the histamine liberator compound 48/80 reduced the carrageenan-induced paw oedema only in the capsaicin-treated rats whereas pretreatment with indomethacin reduced it in both groups of rats. The increased and prolonged inflammatory response to carrageenan in capsaicin-treated rats may be explained by an enhanced release of histamine from mast cells and may also reflect a 'trophic disorder of the denervated skin'.