Abstract. Pulmonary veins (PVs) are important foci of ectopic beats to initiate paroxysmal atrial fibrillation. T-type calcium current (I_Ca-T) has been suggested to contribute to normal and abnormal automaticity of cardiomyocytes. The purpose of the present study was to evaluate whether I_Ca-T plays a role in the electrical activity of PV cardiomyocytes. Whole-cell clamp techniques were used to study Ca²⁺ currents in rabbit PV and atrial cardiomyocytes. L-type calcium current (I_Ca-L) and I_Ca-T were distinguished by voltage dependence of activation. I_Ca-T was identified in 12 of 31 (39%) PV cardiomyocytes with pacemaker activity, 2 of 23 (9%) PV cardiomyocytes without pacemaker activity and 2 of 13 (15%) atrial myocytes (P<0.05). Maximum I_Ca-L and I_Ca-T densities were 6.87±2.17 pA/pF and 1.38±0.69 pA/pF. Nickel (40 mM) did not change the automaticity in 9 (64%) PV cardiomyocytes, but decrease the spontaneous activity in 5 cardiomyocytes (3.1±0.6 Hz versus 2.2±0.5 Hz, P<0.05). Nickel (40 mM) suppressed the amplitudes of DAD (n=4, 13±1 mV versus 7±1 mV, P<0.05) and suppressed the transient inward currents (n=11, 1.2±0.2 pA/pF versus 0.7±0.1 pA/pF, P<0.01). I_Ca-T is present in PV cardiomyocytes and contributes to the pacemaker activity and triggered activity, which are of functional importance in the arrhythmogenesis of PV cardiomyocytes.