Mesenchymal stem cells/marrow stromal cells (MSCs) are ideally suited for cellular therapy due to their ease of isolation, manipulation, and strong safety profile in the clinic. They can be expanded from normal qualified human donors in large quantities and can be infused without tissue matching, since they shield themselves from the immune system. The ability to be transplanted without tissue matching has allowed large multicenter trials to be conducted with direct comparison of the same batches of MSCs, without adverse events or rejection reactions. MSCs are now approved as drugs in several countries outside of the USA. MSCs can be genetically modified to provide sustained and long-term delivery of growth factors at supraphysiological levels. Gene-modified MSCs are in clinical trials for the treatment of stroke and are under consideration for the treatment of neurodegenerative disorders such as Huntington's disease.