The last decade was marked by a revolution in molecular biology, culminating with the Human Genome Project. This revolution has changed the classic practice of clinical cardiology in many ways, increasing our awareness of inheritance of defective genes and their impact on health and disease, and providing new diagnostic and therapeutic tools. On the other hand, identification of new diseases in the clinical setting has triggered research into previously unexplored areas of molecular biology. As a result of this interaction, both fields underwent major paradigm shifts. This article presents a primer of molecular biology for the cardiologist, followed by a discussion of the impact the Human Genome Project will have on the clinical practice of cardiology.