Dopamine cell death is the primary problem limiting the value of neurotransplantation in human patients with Parkinson's disease. To address this problem, we added glial cell line-derived neurotrophic factor (GDNF) to cultures of embryonic dopaminergic neurons obtained from human and from Bonnet monkey (Macaca radiata) in an effort to reduce apoptotic cell death and improve overall cell survival. Tissue from three human embryos, 7-8 weeks post-conception, and one 9-week post-conception monkey embryo were dissociated and cultured in F-12 media with 5% human placental serum. GDNF (10 ng/ml) in human cultures nearly doubled dopamine neuron survival and reduced the rate of apoptosis from 6% to 3%. In monkey cultures, GDNF also enhanced dopamine neuron survival and reduced the apoptotic rate. We conclude that GDNF improves the survival of primate embryonic dopamine neurons in culture by reducing apoptosis.