Intracellular calcium regulation is critically important for numerous cellular functions, such as muscle contraction, secretion, neurotransmitter release and cell migration. Voltage-activated calcium channels play a crucial role in severalof these processes (see Figure 1). Although the functional diversity of calcium channels can be explained by the rich molecular variety of this channel superfamily, a common denominator of calcium channel function is that they all couple incoming excitatory electrical signals to fundamental processes within the cell. Different calcium channel subtypes can play a variety of physiological roles within cells, depending on the stage of development, cell type and other factors. A couple of notable exceptions are the skeletal L-type calcium channel α1s, which is the only calcium channel that coordinates muscle contraction in skeletal muscle, and the L-type channel subtype α1F, whose expression seems to be restricted to retinaltissue.