Strong depolarization pulses facilitate L-type Ca2+ channels in various cell types including cardiac myocytes. The mechanisms underlying prepulse facilitation are controversial with respect to the requirements for channel subunits, cAMP-dependent protein kinase, and additional anchor proteins. The properties of voltage-dependent facilitation of the L-type Ca2+ channel was studied in recombinant cardiac α1 subunits with or without cardiac β subunit, expressed in Chinese hamster fibroblast cells. The magnitude of voltage-dependent IBa facilitation in the α1 subunit channel is dependent on the duration of the prepulse as well as on the interval duration between prepulse and test pulse. The characteristics of this facilitation were not affected by coexpression of the β subunit. These results indicate that cardiac α1 subunits exhibit voltage-dependent facilitation because of their own intrinsic structure, independent of any other accessory subunit or additional regulatory proteins, and that cardiac β subunits have no essential regulatory role at the onset or continuance of the voltage-dependent facilitation.