Cardiac progenitor cells play an important role in cardiac repair and regeneration; however, their cellular biology and electrophysiology are not understood. The present study characterizes the functional ion channels in human cardiac c-kit(+) progenitor cells using whole-cell patch voltage-clamp, RT-PCR, and Western blots. We found that several ionic currents were present in human cardiac c-kit(+) progenitor cells, including a large-conductance Ca(2+)-activated K(+) current (BKCa) in 86 % of cells, an inwardly rectifying K(+) current (I Kir) in 84 % of cells, a transient outward K(+) current (I to) in 47 % of cells, a voltage-gated tetrodotoxin-sensitive Na(+) current (I Na,TTX) in 61 % of cells. Molecular identities of these ionic currents were determined with RT-PCR and Western-blot analysis. KCa.1.1 (for BKCa), Kir2.1 (for I Kir), Kv4.2 and Kv4.3 (for I to), Nav1.3 and Nav1.6 (for I Na.TTX) were abundantly expressed in human cardiac c-kit(+) progenitor cells, which do not resemble cardiomyocytes at all. These results demonstrate for the first time that four types of ionic currents including BKCa, I to, I Kir, and I Na.TTX, are heterogeneously present in human cardiac c-kit(+) cells, which may be involved in regulating cellular physiology.