Neurons in the adult human lateral geniculate nucleus have been classified using Golgi preparations. The neuronal classes correspond to those previously described in monkey (Saini and Garey 1981). The commonest are multipolar neurons with either "radiate" or "tufted" dendritic trees. Also seen frequently are bipolar neurons with two or three diametrically opposed dendrites. Rarer classes include neurons with beaded dendrites and those with "axon-like" dendritic processes, perhaps interneurons. Neurons are also found in the circumgenicule capsule. Most neurons have dendrites restricted to the laminae, but some dendrites cross the borders of both magno- and parvocellular laminae. Somata are also seen in interlaminar zones with dendrites reaching the adjacent laminae. No significant difference, apart from size, is found between neurons in magno- and parvocellular laminae. Most neuronal types are found at birth. They are, however, strikingly different from their adult forms in having growth cones and filopodia and an abundance of dendritic and somatic spines and "hair-like" processes. Morphological maturity is reached by about nine months postnatally. Similar maturational changes occur in monkey in the first two months of life (Garey and Saini 1981) and in both monkey and man this period of maturation of the lateral geniculate nucleus corresponds to increasing visual acuity and a time when each species is most likely to be affected by visual deprivation.