The troponin complex is a group of three protein subunits located on the thin filament of the contractile apparatus. These three subunits—troponin T, troponin I, and troponin C—different in genetic and protein structure, act together to regulate muscle contraction. The distribution, function, and detection of these subunits in different muscle tissue and blood components, as well as their relation to myocardial damage, will be reviewed in this article.