The data from 112 purebred and crossbred goats produced by matings of Korean native goats and Saanen, which were investigated at Livestock Experiment Station since 1963, were analysed by least square method to investigate changes of body weights of the native goats by grading up with Saanen. This procedure adjusted the measurement data for environmental effects of year of birth, age of dam and litter size. The results obtained were as follows; 1. The body weight was measured and adjusted at birth, weaning, 12 and 18 months of age as 1.83㎏, 6.99㎏, 14.51㎏ and 18.90㎏ in Korean native goats, 2.98㎏. 12.25㎏, 25.49㎏ and 36.93㎏ in purebred Sannen, 2.69㎏, 11.14㎏, 23.03㎏ and 29.27㎏ in the first filial generation, and 2.78㎏, 11.85㎏, 24.77㎏ and 36.19㎏ in the second graded generation, respectively. 2. The body weights of first filial and second generation were heavier than those of native goats through all months of age. The increment of body weight in the first filial generation to the native goats was 0.86㎏ at birth, 4.15㎏ at weaning, 8.50㎏ at 12 months and 10.37㎏ at 18 months of age. In the second generation the increment of body weight was 0.94㎏, 4.85㎏, 10.26㎏ and 17.29㎏, respectively. 3. The differences of body weight between purebred Saanen and the first generation were 0.28㎏ at birth, 1.11㎏ at weaning 2.4㎏ at 12 months and 7.6㎏ at 18 months of age, but significant difference was found only at 18 months of age (p$lt;0.01). The body weight of the second generation was slightly lighter by 0.20 to 0.75㎏ than that of purebred Saanen through all months of age. 4. The second generation was heavier than the first generation by 0.08㎏ at birth. 0.71㎏ at weaning, 1.73㎏ at 12 months and 6.92㎏ at 18 months of age, but significant difference was found after 18 months of age (p$lt;0.05).