Abstract: Objective To observe the effect of growth hormone on the expression of collagen Ⅱ of cultured growth plate chondrocytes of rats. Methods Primary chondrocytes from tibial growth plate of 5~8 rats by trypsin-collagenase digestion were cultured in monolayer. RT-PCR and immunocytochemistry were performed to investigate the expression of collagen Ⅱ at the mRNA and protein level, respectively with different concentrations of GH. Results GHenhances the expression of collagen Ⅱ of chondrocytes in vitro in a concentration-dependent fashion. The expression of collagen Ⅱ was obviously between the GH concentration of 10 ng/ml and 500 ng/ml(P<0.05) , maximally at the concentration of 100 ng/ml, and decreased again after higher concentration of GH. There was no significant difference between 1000 ng/ml group and control group(P>0.05 ). Conclusion GH can maintain the phenotype of chondrocytes by enhancing the expression of collagen Ⅱ and it will not increase the bone age during clinical practice.