This monograph contains 20 selected papers presented at the Symposium on Subcellular Basis of Contractile Failure which was held in Ottawa during May 11-13, 1989 and is designed for the benefit ofthose who were unable to attend this event. It is now increasingly becoming clear that an excessive amount of calcium is intimately involved in the pathogenesis of a wide variety of heart diseases. Accordingly, the investigations concerning the role of calcium chan nels and their regulatory mechanisms in heart function as well as of the intra cellular calcium overload in cardiac dysfunction are presented here. Since sodium is also considered to influence the cardiac contractile force by chang 2 ing the intracellular concentration of calcium through the Na +-Ca+ exchange 2 mechanism in the cell membrane, the role of Na +-Ca+ exchange in heart func tion as well as pathology of contractile failure is discussed. In view of the new ly discovered implications of the oxygen free radicals in cellular injury, papers concerning the role of these radicals in heart disease are included in this book. For the purpose of clarity, different chapters have been organized under three main headings: (I) Role of cations in heart function, (II) Cardiac hypertrophy and cardiomyopathies, and (III) Ischemic heart disease and cardiac failure.