The presence of mesenchymal stem cells (MSCs) in human periodontal ligament (PDL) were first described by Seo et al. in 2004. These cells are capable of plastic adherence, colony forming and differentiation into various cell types when cultivated in appropriate cell culture conditions. PDL stem cells are investigated by high number of scientists nowadays because of their high potency for tissue regeneration. However, little is known about the effects of various active molecules and growth factors on their stem cell properties. There is limited number of reports revealing the activity of these cells when applied in clinical studies. The purpose of the current review is to highlight the stem cell properties of human PDL MSCs and to briefly systematize the data from various sources.