To observe the effect of different concentrations of nylestriol (NYL) and levonorgestrel (LNG) on the expression of ERα and ERβ in human osteoscarcoma MG-63 cell lines, and to explore the impact of paracrine effect on the gene expression.MG-63 cells were treated with 3 concentrations (10(-10),10(-8), and 10(-6) mol/L) of NYL or LNG. The untreated control group and the positive control group were also established. The 2 groups treated with NYL (10(-10) mol/L) or LNG (10(-8) mol/L) were designed to renew the medium every 12 h. Semi-quantitative RT-PCR was conducted to detect the mRNA expression of ERα and ERβ on the MG-63 cells treated with different concentrations of the 2 drugs, respectively.Both drugs up-regulated ERα and ERβ mRNA expression. The best concentration for both NYL and LNG was 10(-6) mol/L for ERα expression. As for ERβ, the best concentration of NYL and LNG was 10(-10) mol/L and 10(-8) mol/L. The role of medium replacement on the expression of ERα was not observed, but medium replacement inhibited ERβ expression.Both NYL and LNG can up-regulate the mRNA expression of ER subtypes in MG-63 cells, with mutual restriction between the 2 subtypes. The paracrine effect on MG-63 cell lines may be involved in the regulation process of mRNA expression of ERβ.