Increasing experimental evidence indicates that skeletal myoblasts can be considered as a possible source of cells for regeneration of contractile performance in chronic postinfarction myocardial injury. In experimental models, the observed functional benefit of transplanting skeletal myoblasts into an area of chronic fibrotic myocardial scar has led to the development of clinical trials to evaluate the potential use of autologous skeletal myoblasts for myocardial regeneration in patients with postinfarction heart failure. We conducted an independent, phase I clinical trial to evaluate myoblast transplantation during coronary artery bypass grafting. In addition, to test whether the effect of transplanted cells on myocardial contractility was independent of revascularization, we performed a clinical study of percutaneous transvenous myoblast transplantation-the POZNAN trial. These trials have shown the feasibility of myoblast transplantation during cardiac surgery and via a percutaneous route, as well as the safety of both procedures when performed with concurrent prophylactic administration of amiodarone. Here, we review the details of our observations from both of these phase I clinical trials in the context of the clinical work in cardiovascular cell transplantation performed by others.