Troponin is a central subject in biochemical, biophysical, and physiological research. The discovery of this protein by Professor Setsuro Ebashi in 1965 initiated a new era in research into the molecular biology of the regulation of contraction in striated muscle. Troponin is one of the representative functional proteins in living organisms, and its structure and function have been studied extensively. Recently, the crystallographic structure of troponin ternary complex was determined successfully. Mutations in genes of cardiac isoforms of troponin have been shown to cause cardiomyopathies, and the pathogenic consequences of these genetic disorders are being investigated. In clinical medicine, troponin is now widely utilized as an excellent biochemical marker for myocardial infarction. This volume covers the entire spectrum of research on troponin and related muscle proteins, including pathophysiological and clinical aspects.