Abstract： Objective To investigate the biological role of insulin-like growth factor I(IGF-I) and hyaluronic acid(HA) in human articular chondrocytes. Methods Human articular chondrocytes were isolated and cultured in DMEM. IGF-I , HA as well as both IGF-I plus HA were added into the cultured medium respectively. The proliferation of chondrocytes was measured with MTr method. From passage 4, IGF-I and HA were added into the cultured media. The electron microscopic observation, toluidine blue staining, human collagen Ⅱ and aggrecan immunnhistochemistry, reverse transcript polymerase chain reaction (RT-PCR) were conducted to investigate the phenotype of passage 8 chondrocytes treated by IGF-I and HA. The passage 6 chondrocytes without any treatment was used as control group. Results The addition of 10 μg/L of IGF-I in the culture medium significantly enhanced the proliferation of chondrocytes, and this enhancement was maximal at the concentration of 50 μg/L. The chondrocytes proliferation was not obviously with different concentrations of HA. The combination of IGF-I and HA was stronger promotion of the proliferation than that of HA or IGF-I only, and could prolong the duration of promoting chondrocyte proliferation. There were massive rough surfaced endoplasmie reticulums and secretory vesicles in cytoplasm by electron microscopic observation. RT-PCR revealed positive collagen Ⅱ mRNA and negative collagen Ⅰ. Toluidine blue staining showed metachromia granule. Collagen Ⅱ and aggrecan immunohistochemistry showed 92% positive cell in the passages 8 chondrocytes. Its gray scale displayed distinctively stronger than control group. Conclusions IGF-I can promote the proliferation of human articular chondrocyte,but HA can not. When IGF-I and HA are combinated together, the ability of promoting the proliferation of chondrocytes is stronger and it can keep the hyaline condrocyte phenotype more stable.