Point of View. Long QT syndrome type 1 (LQFI) causes torsades de pointes arrhythmia, ventricular fibrillation, and sudden death. It usually is inherited as an autosomal dominant trait (Romano‐Ward syndrome). The primary defect in LQTI is a mutation in KVLQT1, a gene that encodes the pore‐forming α‐subunit of a K⁺ channel. KvLQT1 α‐subunits coassemble with minK β‐subunits to form channels that conduct the slow delayed rectifier K⁺ current (I_Ks) in the heart. Recessive mutations in KVLQT1 cause Jervell and Lange‐Nielsen syndrome, which is characterized by more severe arrhythmias and congenital neural deafness. Heterologous expression studies demonstrated that mutations in KVLQT1reduce I_Ks by causing loss of channel function, altered channel gating, and/or a dominant‐negative effect. It remains to be proven that an understanding of the molecular basis of LQT1 will lead to more effective therapy.