Aging can be viewed partly as a degenerative process dictated by free radical reactions. Human diploid fibroblasts (HDFs) lose the capacity to proliferate and enter a state termed replicative senescence after a finite number of population doublings in vitro. Presenescent human fibroblasts, when treated with a sub-lethal dose of H2O2, enter long term growth arrest resembling replicative senescence. H2O2 induced growth arrest; p53 protein expression and the effect of vitamin C as an antioxidant were determined in this study.