Whole-cell and single-channel calcium currents in enzymatically isolated dog saphenous vein cells were recorded by the patch-clamp method. Test pulses to negative potentials from holding potentials of −90 to −40 mV elicited currents that inactivated quickly and in a voltage-dependent manner (called Ilowfor low threshold). A second calcium current persisted even at relatively positive holding potentials of − 30 to −10 mV, required stronger depolarizations for maximum current, and inactivated slowly (Ihighfor high threshold). Ihightransported barium more than calcium, whereas Ilowtransported the two ions equally. Single-channel current records (90 mM barium) showed a larger conductance that activated at relatively positive potentials and a smaller (about one-third) conductance that activated at weak depolarizations. Nitrendipine suppressed Ihigh, and the effect was voltage dependent as observed in cardiac cells, although block of resting channels was much greater in vein cells (KR±10−8M). Exposure to the stereoisomer (−)Bay K 8644 increased Ihighbut not Ilow. The (−)Bay K 8644 also increased the channel activity and prolonged the open time of the larger conductance current. Thus, two types of calcium channels, differing in potential-dependence of activation and inactivation, calcium/barium selectivity, single-channel conductance, and sensitivities to dihydropyridines were identified in smooth muscle cells isolated from a large cutaneous vein.