Objective To observe the effect of hyaluronic acid on the proliferation of and tyrosinase activity in melanocytes.Methods Normal primary human melanocytes were isolated from infant foreskin tissue and cultured.Different concentrations(0 to 10 g/L)of hyaluronic acid wero added to the culture medium immediately or 8 hours after the inoculation of melanocytes.MTT assay was performed to detect the proliferation of melanocytes,and tyrosinase activity was determined to evaluate the effect of hyaluronic acid on the melanin synthesis by melanocytes.Results The proliferation level (absorbance at 490 am,A490)of melanocytes was 0.14±0.02,0.37±0.08,0.45±0.11,0.49±0.07,0.55±0.12,0.52±0.11,0.49±0.07,0.39±0.05,0.19±0.03 and 0.01 4-0.01 when treated with hyaluronic acid of 0,0.008,0.016,0.313,0.625,1.250,2.500,5.000,7.500 and 10.000 g/L,respectively.The hyaluronic acid of 0.08 to 5 g/L markedly accelerated the proliferation of melanocytes,while that of 10 g/L inhibited their proliferation.The tyrosinase activity in melanocytes was promoted by hyaluronie acid of 0.2 to 5 g/L,but suppressed by that of 10 g/L.The proliferation of melanocytes treated with hyaluronic acid immediately after the inoculation was more rapid than that treated with hyaluronic acid 8 hours after the inoculation.Conclusion The hyaluronic acid of 0.2 to 5 g/L can enhance the proliferation of and tyrosinase activity in melanocytes.