The ascending efferent projections of the neurons of the anterior (LHAa), central (LHAc) and posterior (LHAp) parts of the lateral hypothalamic area (LHA) have been studied using an autoradiographic analysis of the anterograde axonal transport after local injection of tritiated amino acids. Our results show that LHA regions have common projections particularly to the thalamus and to the hypothalamus. They also demonstrate the existence of differential projections: i.e. an anteroposterior gradient of projection sites according to anterior, central and posterior localisation of the LHA neurons. The LHAa neuronal projections terminate in the lateral septal area; the LHAc projections innervate the frontal cortex while LHAp neurons send their projections to the olfactory bulb and innervate both the cerebral cortex and the hippocampus. Only the LHAp neurons project measurably to the globus pallidus, the caudate putamen and the nucleus accumbens.