Low-voltage-activated calcium channels, also known as T-type calcium channels, are widely expressed in various types of neurons. In contrast to high-voltage-activated calcium channels which can be activated by a strong depolarization of membrane potential, T-type channels can be activated by a weak depolarization near the resting membrane potential once deinactivated by hyperpolarization, and therefore can regulate the excitability and electroresponsiveness of neurons under physiological conditions near resting states. Recently, the molecular diversity and functional multiplicity of T-type channels have been demonstrated through molecular genetic studies coupled with physiological and behavioral analysis. Understanding the functional consequences of modulation of each subtype of these channels in vivo could point to the right direction for developing therapeutic tools for relevant diseases.