Medium spiny neurons (MSNs) are GABA-ergic striatal projection neurons, which degenerate in Huntington's disease (HD), a neurological disorder associated with motor and cognitive dysfunctions. Using an efficient protocol for the differentiation of human embryonic stem (ES) and induced pluripotent stem (iPS) cells, we were able to generate MSNs exhibiting molecular hallmarks similar to those expressed by endogenous MSNs. Electrophysiological properties of mature neurons were studied by means of patch-clamp whole-cell recordings. During depolarizing current step the majority of hES/hiPS cells showed a repetitive firing, a slow depolarization and a delay in the first spike generation, typical of rat MSNs. To test the expression of functional GABAergic receptors, GABA-evoked currents were observed in a large number of derived cells. Due to the main role of dopamine (DA) in modulating MSN activity, DA application reduced the GABA-evoked current; moreover application of quinpirole, a selective D2 agonist, affected the resting membrane potential and the cell excitability, acting on some classes of K⁺ channels. To assess the cell viability in vivo, hES-derived neurons were grafted into fetal rat brains. Electrophysiological recordings from brain slices confirmed that differentiated neurons were able to mature and integrate in the host tissue. These results suggest that hPS cells can be driven to acquire a striatal fate, using a powerful tool for future regenerative medicine.