Abstract It has been shown that leukaemia previously that inhibitory factor (LIF) transforming and growth factor-α (TGF-α) stimulate proliferation of primary culture of murine myoblasts. We now show that human myoblasts respond in a similar manner to LIF and TGF-α. These responses occur over a range of growth conditions. There are total additive effects in both human and murine myoblasts between LIF and TGF-α and LIF and fibroblast growth factor-β (FGF-β), but not between LIF and interleukin-6 (IL-6) or insulin-like growth factor 1 (IGF-1). The LIF response is initiated by a short exposure to the cytokine and is maintained for prolonged periods in its absence.