Skeletal muscle, adipose tissue and liver are the quantitatively major targets for insulin action in vivo and regulation of critical steps in intermediary metabolism within these tissues account for many of the impacts of insulin on metabolic homeostasis. Many other tissues including the heart express insulin receptors and their functions may be importantly regulated by insulin. In this review we summarize the evidence that the heart is an important target of insulin action and that abrogation of these actions is important in disease states. Current understanding of the molecular basis of insulin actions on its target cells is drawn from a large literature emanating from studies of the major target tissues and also from a wide range of other cell types including studies of wx appropriately transfected and immortalized cell lines 1–4. We introduce the basic concepts of the molecular basis of insulin actions, not to reiterate the extensive reviews recently published but rather to highlight aspects which are distinctive or which are poorly-defined in the heart. Our understanding of the biochemical mechanisms by which insulin exerts its effects in the heart are still substantially dependent upon extrapolation from studies of other cell types. It is important to recognize where such extrapolations may require qualification; we therefore focus particularly on the specific features of the myocardium which may lead to a distinct perspective of insulin action in this tissue.