 Stem cell therapy holds great promise for treating degenerative diseases, cancer, and tissue damage, but also poses potential risks that must be carefully evaluated before clinical use. The risk profile of stem cell-based medicinal products depends on factors such as the type of stem cells, their differentiation status, proliferation capacity, route of administration, intended location, in vitro culture, and other manipulation steps. Tumor formation, unwanted immune responses, and transmission of adventitious agents are potential risks associated with pluripotent stem cells, embryonic stem cells, and induced pluripotent stem cells, while mesenchymal stem, stromal cells, master of science, have shown relatively safe results in small-sized clinical trials. However, serious adverse events have been reported in some master of science trials, highlighting the need for further knowledge on biological mechanisms and long-term safety. This article was authored by Hermsson-Harmph, Cormus LSG and Herbert Scala A.