Molecular cloning of the low voltage-gated, T-type, calcium channel family opened new avenues of research into their structure-function, distribution, pharmacology, and regulation. Cloning of mammalian cDNAs led to the identification of three T-channel genes: CACNA1G, encoding Cav3.1; CACNA1H, encoding Cav3.2; and CACNA1I, encoding Cav3.3. This allowed sequencing of these genes in absence epilepsy patients, and the identification of single nucleotide polymorphisms (SNPs) that alter channel activity. Their distribution in thalamic nuclei, coupled with the physiological role they play in thalamic oscillations, leads to the conclusion that SNPs in T-channel genes may contribute to neurological disorders characterized by thalamocortical dysrhythmia, such as generalized epilepsy. This section reviews the structure of T-channels, how splicing affects structure and function, how SNPs alter channel activity, and how high voltage-activated auxiliary subunits affect T-channels.