Currently fewer than 50% of UK lambs produce carcasses of acceptable quality for the domestic and export markets, which compromises the competitiveness of sheep farming. Carcass quality can be changed by selection, and this is now being taken advantage of in terminal sire breeds and, to a lesser extent, in hill breeds. However, little attention has yet been focused on the crossing breeds, which have relatively poor carcass quality, in spite of the large impact such breeds have on the slaughter generation. Recently, a long-term project began to develop breeding programmes relevant to crossing sire (‘longwool’) breeds. Its objective is to produce a selection index to improve carcass quality without compromising the reproductive performance or maternal ability of these breeds. The Bluefaced Leicester is the most prevalent crossing sire breed with its crossbred (‘Mule’) daughters out of draft hill ewes accounting for 89% of crossbred (longwool x hill) ewes in the UK (Pollot, 1998).