Summary Thousands of patients and placebo-treated controls have been included in many clinical trials of stem cell therapy over the last decade or so, but often the study groups have been small. Their scientific value may therefore be limited and their ethical justification questionable. Would “crowd sourcing” for data sharing be a means of increasing the collective value of clinical trials? Here, we make a case for open access of all data emerging from stem cell studies (trials but also observational studies) independent of whether they are investigator-initiated or commercially driven.