Three groups of rats received unilateral injections of ibotenic acid, 6-hydroxydopamine or vehicle control into the lateral hypothalamic area, and were given a range of tests of sensorimotor capacity. As expected from previous reports, the 6-hydroxydopamine injections induced a marked sensorimotor impairment to the contralateral side of the body. By contrast, the ibotenic acid injections produced no detectable sensorimotor changes, although the parameters and histological extent of the lesion were identical to those which produce aphagia, adipsia and sustained regulatory impairments when administered bilaterally. These results dissociate the classic electrolytic lesion of the lateral hypothalamus into homeostatic impairments following damage to intrinsic hypothalamic neurones, and sensorimotor impairments dependent only on damage to passing catecholamine fibre systems.