We previously identified a stromal cell-derived inducing activity (SDIA), which induces differentiation of neural cells, including midbrain tyrosine hydroxylase-positive (TH⁺) dopaminergic neurons, from mouse embryonic stem cells. We report here that SDIA induces efficient neural differentiation also in primate embryonic stem cells. Induced neurons contain TH⁺ neurons at a frequency of 35% and produce a significant amount of dopamine. Interestingly, differentiation of TH⁺ neurons from undifferentiated embryonic cells occurs much faster in vitro (10 days) than it does in the embryo (≈5 weeks). In addition, 8% of the colonies contain large patches of Pax6⁺-pigmented epithelium of the retina. The SDIA method provides an unlimited source of primate cells for the study of pathogenesis, drug development, and transplantation in degenerative diseases such as Parkinson's disease and retinitis pigmentosa.