Stem cell treatment for acute or chronic ischemic myocardium has gained major attention in the last decade. Experimental and clinical studies have shown evidence for functional improvement after cell-based treatments in acute or chronically ischemic jeopardized myocardium. Since 2001 we have performed bone marrow-derived CD133+ stem cell transplantations with concomitant coronary artery bypass surgery. Although our focus is mainly on the functional results of the stem cell treatment, possible long-term side effects of the new therapeutic strategy should also be addressed. Here we present for the first time the long-term follow-up safety results of the Rostock trial after direct intramyocardial stem cell treatment in 32 patients.