Morphological, histochemical and electrophysiological studies were made on human fetal central nervous tissue maintained for up to 56 days in vitro. It was observed that most of the neurones and glial cells in spinal cord and brain stem cultures are more differentiated than those in cultures of cerebellum and cerebral cortex. AChE-containing neurones could be demonstrated in cultures of spinal cord. Intracellular microelectrode recordings were made on neurones of spinal cord and brain stem cultures. The membrane potentials recorded from spinal neurones ranged from –25 to –60 mV with an average of –44 mV. An increase of the extracellular potassium concentration (50 mM) caused a depolarization of the cell membrane similar to that observed in neurones of rat spinal cord cultures.