The subthalamic nucleus (STN) plays a key role in motor control. Although previous studies have suggested that Ca²⁺ conductances may be involved in regulating the activity of STN neurons, Ca²⁺ channels in this region have not yet been characterized. We have therefore investigated the subtypes and functional characteristics of Ca²⁺ conductances in STN neurons, in both acutely isolated and slice preparations. Acutely isolated STN cells were identified by retrograde filling with the fluorescent dye, Fluoro-Gold. In acutely isolated STN neurons, Cd²⁺-sensitive, depolarization-activated Ba²⁺ currents were observed in all cells studied. The current-voltage relationship and current kinetics were characteristic of high-voltage–activated Ca²⁺channels. The steady-state voltage-dependent activation curves and inactivation curves could both be fitted with a single Boltzmann function. Currents evoked with a prolonged pulse, however, inactivated with multiple time constants, suggesting either the presence of more than one Ca²⁺ channel subtype or multiple inactivation processes with a single channel type in STN neurons. Experiments using organic Ca²⁺ channel blockers revealed that on average, 21% of the current was nifedipine sensitive, 52% was sensitive to ω-conotoxin GVIA, 16% was blocked by a high concentration of ω-agatoxin IVA (200 nM), and the remainder of the current (9%) was resistant to the co-application of all blockers. These currents had similar voltage dependencies, but the nifedipine-sensitive current and the resistant current activated at slightly lower voltages. ω-Agatoxin IVA at 20 nM was ineffective in blocking the current. Together, the above results suggest that acutely isolated STN neurons have all subtypes of high-voltage–activated Ca²⁺ channels except for P-type, but have no low-voltage–activated channels. Although acutely isolated neurons provide a good preparation for whole cell voltage-clamp study, dendritic processes are lost during dissociation. To gain information on Ca²⁺ channels in dendrites, we thus studied Ca²⁺ channels of STN neurons in a slice preparation, focusing on low-voltage–activated channels. In current-clamp recordings, a slow spike was always observed following termination of an injected hyperpolarizing current. The slow spike occurred at resting membrane potentials and was sensitive to micromolar concentrations of Ni²⁺, suggesting that it is a low-threshold Ca²⁺ spike. Together, our results suggest that STN neurons express low-voltage–activated Ca²⁺ channels and several high-voltage–activated subtypes. Our results also suggest the possibility that the low-voltage–activated channels have a preferential distribution to the dendritic processes.