OBJECTIVE To explore the potential of murine bone marrow stromal cells (MSCs) to differentiate into vascular smooth muscle cells so as to contribute to neointimal formation after vascular injury. METHODS Murine MSCs were isolated from bone marrow and cultured in M199 with 10% FBS supplemented with medium conditioned from human smooth muscle cell culture to induce differentiation. Immunofluorescent technique was used to observe the morphology of cells to examine the smooth muscle characters. Vasoactive substance was added onto the cultured smooth muscle-like cells. Inverted microscopy was used to observe the contractile changes of the cells. RESULTS After 6 passages of subculture in differentiation medium, MSCs demonstrated smooth muscle cell-like spindle-shaped morphology and assumed a hill-and-valley growth pattern. Immunofluorescent technique revealed positive signals for alpha-smooth muscle actin, calponin and smooth muscle myosin heavy chains. The smooth muscle cell-like cells displayed robust calcium transients. In response to stimulation of vasoactive substance the [Ca(2+)] of the cells instantaneously increased which was coupled by prominent cell contraction. CONCLUSION MSCs can differentiate into vascular smooth muscle cells with contractile ability. This model may be useful in study of smooth muscle cell differentiation and the origin of neointimal cells after vascular injury.