The differentiation of skeletal muscle is commonly examined in cell culture using the C2C12 line of mouse skeletal myoblasts. This process shares many similarities with that which occurs during embryonic development, such as the transient activation of caspases. Here, we examined the effect of inhibiting mitochondrial fission, using mdivi-1, on the ability of C2C12 cells to terminally differentiate. This was performed using immunofluorescent identification of cell morphology and myosin expression, as well as immunoblotting for markers of muscle differentiation. Furthermore, the effect of mdivi-1 administration on activation of caspase-2 and -3 was assessed using spectrofluorometric measurement of specific enzyme activity.