The additive and heterosis effects on body weights between Hanwoo(Korean cattle) and crossbreeds from Charolais x Hanwoo were estimated. The data were recorded from 1979 to 1991 in Kangwha area and were analysed by using linear regression models. The estimated least squares means on body weights of Hanwoo were 85.4±4.6 ㎏ at 3 months of age. 150.2±6.9 ㎏ at 6 months of age and 258.5±11.4 ㎏ at 12 months of age, respectively. The body weights of the crossbreeds ranged from 117.1 to 126.3㎏ at 3 months of age, from 192.0 to 216.8 ㎏ at 6 months of age, and from 352.6 to 383.4 ㎏ at 12 months of age, respectively. The additive effects on body weight were 45.59±6.37 ㎏ at 3 months of age, 78.75±10.13 ㎏ at 6 months of age and 136.27±17.69 ㎏ at 12 months of age. The effects of heterosis were 7.65±3.89 ㎏ at 3 months of age, 21.35±6.09 ㎏ at 6 months of age and 47.47±10.92 ㎏ at 12 months of age, respectively.