The aim of the present study was to evaluate the possible beneficial effects of implantation of laser-irradiated mesenchymal stem cells (MSCs) into the infarcted rat heart. MSCs were isolated from rat bone marrow and grown in culture. The cells were laser irradiated with Ga-Al-As laser (810 nm wavelength), labeled with 5-Bromo-2'deoxyuridine (BrdU), and then implanted into infarcted rat hearts. Non-irradiated cells were similarly labeled and acted as control. Hearts were excised three weeks later and cells were stained for BrdU and c-kit (Stem cell marker) immunoreactivity. Infarcted hearts that were implanted with laser-treated cells showed a significant reduction of 53% in infarct size and a 5-6.3-fold significant increase in cell density that reacted positively to c-kit. The findings of the present study provide the first evidence that LLLT can significantly increase survival and/or proliferation of MSCs post implantation into the ischemic/infarcted heart, followed by a marked reduction of scarring, and enhanced angiogenesis.