There is great reason for optimism in the field of research into the long QT syndrome (LQT). We have made considerable progress, but there is much more to be done. We used molecular genetics to identify genes responsible for 2 forms of LQT (cardiac potassium and sodium channel genes HERG and SCN5A, respectively). These discoveries have led to improved mechanistic undertaking of the disorder and created the possibility for genetic testing. We are working to develop genetic tests for autosomal dominant LQT, but this will require identification of additional LQT genes. Specialized research laboratories like ours can provide genetic testing for many families, but these tests are not yet generally available. These tests may be particularly useful for families with LQT, since asymptomatic LQT gene carriers are still at risk for sudden death. Finally, molecular genetic and physiologic studies offer the possibility of new strategies for treatment and prevention of this cardiovascular disease.