The effects of aging on human mesenchymal stem cells, (MSC) were investigated. MSC were isolated from patients of different ages and the different parameters of aging were measured either immediately after isolation or after long-term cultivation in vitro. Markers of senescence were investigated, including p21, p53 and beta-galactosidase levels. Antioxidative defense capacity of the MSC were tested together with markers of oxidative damage and antioxidative enzyme activities. Also the changes in differential potential and numbers of MSC were investigated.