It is possible to grow functional primary dissociated cultures and explants from stereotactic biopsies of human parkinsonian caudate nuclei. Two major classes of cells were identified on morphological grounds. The culture cells appear to be stimulated by an unidentified soluble factor(s) obtained from human fetal neuronal cells in vitro. Culture of primary neuronal and glial cells from human adult cerebral nuclei seems to be a useful tool for several research purposes and in particular for studying both trophic factor action and target effects on afferent neurons for prospective human brain grafting.