The Institute of Medicine and the National Academy of Sciences co-hosted this workshop with the International Society for Stem Cell Research in order to take a critical look at the practice of unproven stem cell treatments. Speakers examined the evidence base of unsubstantiated treatment offerings and the associated research and clinical risks and concerns. Discussions delved into legal hurdles for establishing standards and criteria to govern stem cell trials and treatments and explored a range of potential solutions for assuring the quality of unregulated therapies.