Heart disease remains the leading cause of morbidity and mortality in the developed world, despite significant surgical and pharmacological advances in its treatment. The use of stem cells for cardiac repair and/or cardiac regeneration in heart failure has been intensely studied for the past decade. While clinical trials using various stem cell sources for the treatment of ventricular dysfunction and myocardial repair have demonstrated the safety of both allogeneic and autologous cells, the functional results remain modest, suggesting that a good deal of work needs to be done to improve their therapeutic capacity. Learn the major hurdles remaining and progress to date, specifically with the novel cardiosphere/cardiac progenitor cell source.