Heritabilities of birth weight and weaning weight at 90 days of age were estimated from the analysis of variance using the data from 311 lambs of Corriedale sheep raised at the Alpine Experiment Station from 1966 through 1974. Heritability estimates obtained were 0.21 for birth weight and 0.26 for weaning weight at 90 days of age. The result obtained in this study suggests that the weaning weight can be considered as an important trait in the selection of lambs at weaning age.