This study was undertaken to estimate the effects of year, breed, age of dam, sex of lamb and type of birth on the birth, weaning and grease fleece weights of sheep. The data used were the records of 1,530 heads of Corriedale and Polwarth raised at National Animal Breeding Institute from 1987 to 1988. The effects of year, breed, age of dam, sex of lamb and type of birth on the birth, weaning and grease fleece weight were significantly differed(p $lt;0.01). In the body weight as well as grease fleece weight, the Corriedale and single were heavier than the other side. Maximum body weight and fleece weight were reached at 5∼6 years of ewe age.