Biglycan, a member of the small leucine rich proteoglycan family, is known to be expressed in almost every tissue of our body. Although there are increasing amount of data on the biological role of biglycan, its cardiac function is still not totally clarified. Cardiac protein profiling of biglycan transgenic mice and other studies revealed its involvement in heart failure, myocardial remodeling, and a possible role in promoting cardioprotection. The localization of biglycan on the cell surface and its "pericellular" arrangement as well as the presence of reactive GAG chains on its surface suggest an involvement in transmission of extracellular signals to intracellular signaling molecules and a role in regulation of Ca(++) trafficking. In this review, the role of biglycan in the heart under normal physiological as well as pathological conditions is summarized and critically discussed.