Experimental peripheral inflammation results in cutaneous mechanical hypersensitivity, and repeated low intensity mechanical stimulation of the inflamed skin induces a progressively incrementing hyperalgesia. We have now examined whether the elevation in nerve growth factor (NGF) induced by the inflammation contributes to this progressive hyperalgesia. An i.p. injection of anti-NGF antiserum (5 microliters g-1) 1 h before induction of inflammation by intraplantar complete Freund's adjuvant (CFA) injection and 24 h after, both reduced the basal inflammatory hypersensitivity and significantly attenuated the progressive increase of spontaneous activity, touch-, pinch- and A beta-afferent-evoked responses, and the progressive reduction of the mechanical threshold of biceps femoris/semitendinosus alpha motoneurones normally evoked by repeated (every 5 min) tactile stimulation of the inflamed hindpaw, in decerebrate-spinal rats. NGF contributes, therefore, to the progressive tactile hyperalgesia elicited by repeated touch stimulation of inflamed tissue.