Using a preadipocyte cell line constitutively expressing cMyc, we set out to determine if the ability of cMyc to inhibit adipogenic differentiation was functionally distinct from its role in cell cycle progression and transformation. We now report that in this system differentiation control and cellular transformation are separable functions of cMyc. Furthermore, the Myc-induced inhibition of adipocyte differentiation appears to be mediated via suppression of C/EBP-α and p21 gene expression late in the adipogenic differentiation programme, without deregulation of either cell cycle control or gene expression during the early stages of the process.