Sex steroids have a great influence on bone maturation in childhood, especially in adolescence. However, the precise mechanisums are not fully understood. Human chondrosarcoma-derived chondrocytic cell line HCS2/8 cells were cultured in DMEM culture medium supplemented with 1% fetal calf serum, 1×10(-7) M testosterone or estradiol for 24 hours in a subconfuluent state. Then the cells were pulse labeled with (3)H-thymidine to measure DNA synthesis. In addition, S1 nuclease protection assay of insulin-like growth factor (IGF)-Ⅰ,-Ⅱ and IGF-binding protein (IGFBP)-2, -3, -4 and IGFBP-5 mRNA was carried out. DNA synthesis of HCS2/8 cell was enhanced in the presence of teststerone but not in the presence of estradiol. Using S1 nuclease protection assay, testosterone increased expressions of IGF-Ⅰ,-Ⅱ, and IGFBP-3mRNA. However, estradiol decreased the expression of IGF-Ⅱ mRNA but did not change expressions of IGF-1, IGFBP-2, -3, -4 or IGFBP-5 mRNA. In conclusion, the present results indicate that teststerone stimulates the growth of chondrocytes, probably via increased expressions of IGF-Ⅰ,-Ⅱ, and IGFBP-3 mRNA.