Future improvements in British lamb sales depend on increasing the lean to fat ratio in cuts and joints offered for sale, since numerous surveys have shown an aversion to fat on the part of consumers. This ratio can be changed by manipulating breed and live weight at slaughter, since breeds of large mature size slaughtered at light weights are considerably leaner than those of small mature size slaughtered at heavy weights. However, there are other aspects of carcass value than overall lean and fat content. These include factors such as the proportions of individual joints and their composition. This study was carried out to examine carcass composition and carcass quality changes between 12 and 24 kg cold carcass weight (CCW) in 317 castrated males and 238 females from six pure breeds.