Chondrocytes from the lateral trochlear ridge of the distal femur taken from 1-day-old piglets were cultured in medium supplemented with 0, 7.8, 15.6, 31.2, and 62.5 μmol/L copper. Insulin-like growth factor-1 (IGF-1) and IGF-binding protein 3 (IGFBP-3) levels in culture medium were determined by radioimmunoassay. DNA synthesis in chondrocytes was measured by tritiated thymidine ((3)H-TdR) incorporation. Proliferation-promoting activity and incorporation of (3)H-TdR in chondrocytes were increased in all culture media supplemented with copper and 15% fetal calf serum (FCS). The contents of IGF-1 and IGFBP-3 were also enhanced significantly in culture media containing 15% FCS and supplemented with copper at 15.6, 31.2, and 62.5 μmol/L. The optimal copper concentration for promoting chondrocyte proliferation and autocrine secretion of IGF-1 and IGFBP-3 was 31.2 μmol/L.