In the past decades our understanding of stem cell biology has increased tremendously. Many types of stem cells have been discovered in tissues of which everyone presumed were unable to regenerate in adults; these include particularly the heart and the brain. There is vast interest in stem cells from biologists and clinicians who see the potential for regenerative medicine and future treatments for chronic diseases like Parkinson, diabetes and spinal cord lesions based on the use of stem cells and entrepreneurs in biotechnology who expect new commercial applications ranging from drug discovery to transplantation therapies. As is often the case in science, many early claims turned out to be different from those expected. Embryonic stem cell therapies have not moved rapidly into clinical practice. Adult stem cells certainly have given certain degrees of success but not nearly to the extent that advocates would have wished for. Some claims of early successes in adult stem cell therapies have not been sustained in double-blinded, randomized clinical trials. Some claims are now close to routine therapy. Some of the claims not supported by evidence have nevertheless reached private clinical practice so that "stem cell tourism" is beginning to reach exaggerated proportions