Cultured spinal cord (SC) and dorsal root ganglion (DRG) neurones of 11-13 day old foetal mice were investigated electro-physiologically during differentiation in vitro using the whole-cell patch-clamp technique. High-voltage-activated calcium currents (HVA) and low-voltage-activated (LVA) calcium currents were measured using barium ions as charge carrier. During differentiation in vitro the soma diameter of SC-neurones increased with age (0-42 days in vitro) from 10.3 +/- 2.7 microns to 25.1 +/- 5.9 microns. The capacitance of the soma increased from 7.4 +/- 2.3 pF to 34 +/- 6 pF. The inward calcium current amplitudes increased from 200 pA to 3 nA, while the LVA current amplitude increased only from 50 pA to 100-150 pA. The currents per membrane area through HVA calcium channels increased in the investigated time while the currents through LVA channels decreased.