Reactive oxygen species (ROS) play essential roles in apoptosis and in the regulation of several transcription factors under both physiological and pathological conditions. However, the effects of ROS on MSCs are not well known, and therefore we have investigated the effects of preconditioning with hydrogen peroxide (H 2 O 2 ) on the level of expression of the chemokine receptor, CXCR4, stromal cell-derived factor-1α (SDF-1α)-dependent migration and apoptosis in MSCs. Preconditioning with 20μM H 2 O 2 significantly increased the level of expression of CXCR4 mRNA and protein, and MSCs migration toward SDF-1α; increased expression of CXCR4 and SDF-1α-induced MSCs migration was attenuated by extracellular signal-regulated kinase (ERK) inhibitor PD98059. Preconditioning with 20μM H 2 O 2 significantly protected MSCs against apoptosis induced by 500μM H 2 O 2 . These results suggest that preconditioning with H 2 O 2 can increase MSCs migration toward SDF-1α and protect MSCs against apoptosis.