Abstract: The present invention relates to a method for inducing myocardial cell proliferation. It is based, at least in part, on the discovery that adult human myocardial cells may be induced to proliferate in culture by exposure to a platelet freeze/thaw extract. The present invention provides for a method for inducing myocardial cell proliferation in vitro, as well as for myocardial cell cultures produced by this method. In a preferred embodiment, the invention provides for human myocardial cell cultures. The myocardial cell cultures of the invention may be used to study the physiology of cardiac muscle. In addition, they may be used to identify pharmaceutical agents that may be useful in the treatment of heart disease or, alternatively, agents that are cardiotoxic. Furthermore, the cultures of the invention may be used to provide myocardial cells that may be transplanted or implanted in a patient that suffers from a cardiac disorder.