To determine the role of recombinant human ciliary neurotrophic factor (rhCNTF) in myogenesis, we observed the effects of rhCNTF (0 10 ng/ml) on myoblast differentiation of adult human in vitro. The results showed that compared with the control group, the groups of 2.5 10 ng/ml rhCNTF treatment significantly inhibited myoblast differentiation (P<0.01), and the inhibition was dose-dependent and reversible. Western blots also indicated that compared with the control group, the expression of myogenin and p21, markers of myoblast differentiation phase, was significantly reduced (P<0.01), while Myf5 and desmin, markers of myoblast proliferative phase, significantly increased (P<0.01) in the groups of 2.5 10 ng/ml rhCNTF treatment. These findings demonstrate that exogenous rhCNTF can reversibly inhibit differentiation but permits proliferation of adult human myoblasts in vitro.