Stem cell therapies show great promise, but as yet the vast majority of that promise has not been validated in rigorous clinical trials. Unfortunately, for-profit stem cell clinics are running clinical trials that require patients to pay to be part of them (“pay-to-play”). These trials are not rigorous. Even more unfortunately, it appears that some universities are also running “pay-to-play” clinical trials that bear an uncomfortable resemblance to those run by for-profit clinics.