Background: Mesenchymal stem cells (MSC) are self-renewing clonal progenitor cells of nonhematopoietic tissues that exhibit a marked tropism to wounds and tumors. The authors' studies aimed at exploring how local anesthetics would affect MSC biology. Methods: Proliferation, colony formation, in vitro wound healing, and bone differentiation assays of culture-expanded bone-marrow-derived murine MSC were performed in the presence of increasing concentrations of lidocaine, ropivacaine, and bupivacaine. Cytotoxicity was monitored by measuring lactate dehydrogenase activity and phosphatidylserine exposure/ propidium iodide staining (early apoptotic cells/necrotic cells). Measurements of mitochondrial function in intact and permeabilized cells, transcriptional changes, and changes in nuclear factor -light-chain-enhancer of activated B cells signaling in