Non-invasive methods for the assessment of distribution, homing, and retention of stem cells are desired for the successful demonstration of stem cell therapy. Cells labeled with ^99mTc, ¹⁸F, and ¹¹¹In have been reported for tracking the cells in vivo. However, they can be tracked only for a limited time due to the short half lives of these isotopes. In this context, stem cells labeled with ⁵¹Cr would be appropriate for tracking cells for a longer period of time owing to their half life of 27.7 days. Here, we have isolated mesenchymal stem cells (MSCs) from umbilical cord tissue, characterized them, and attempted to radiolabel them with ⁵¹Cr for mapping the fate of transplanted MSC cells after an intravenous injection via the tail vein in small animals.