Factors which affect the carcass composition of beef cattle include breed type, plane of nutrition and slaughter weight. With increasing weight, the relative proportions of the carcass joints and tissues change and if these changes were known or could be predicted then cattle could be slaughtered at the desired carcass composition. Dairy bred calves for beef production can be classified into three breed categories -straightbred Friesians, early maturing beef breed x Friesians and late maturing beef breed x Friesians. The objectives of the present study were to compare the changes in carcass composition associated with changes in slaughter weight in Friesian (FF), Hereford x Friesian (HF) and Charolais x Friesian (CF) steers and to determine the effects of dietary metabolisable energy (ME) content.