In neurons enzymatically isolated from adult rat dorsal root ganglia and used during the following 24 hours, the Ca²⁺ currents were investigated with the whole-cell patch-clamp technique. In contrast to the neonatal neurons, the salient feature of these adult neurons is the well separated (in the voltage-range) activation and inactivation properties of each recorded current. The low-threshold T-, the high-threshold inactivating N-, and the long-lasting L-currents have a threshold for activation at −60, −45 and −10 mV, and a 50% inactivation at −75, −45 and −5 mV respectively. The N and L currents were poorly affected by 100 μM Ni, a known blocker of T channels and completely blocked by 100 μM Cd²⁺. Frequently we could find neurons with only one type of current present. We conclude that adult sensory neurons are a better preparation for studying, in isolation, the physiological relevance of the three types of Ca²⁺ channels.