In the present work, half carcasses of lambs belonging to the Protected Geographical Indication 'Lechazo de Castilla y León', from the three different authorized breeds: 'Churra, Castellana and Ojalada' have been studied. The half carcasses were measured: carcass weight, chest depth, side length, leg length; anatomical joints were obtaining: pelvic limb, thoracic limb, loin, neck, and distal abdominal and thoracic region; joints were dissected: thoracic and pelvic limbs, obtaining muscle or loin, fat, and bone and other tissues. Also, physical and chemical muscular parameters were determined: pH and mioglobin content. Significant differences between breeds were observed in some determinations (half carcass weight and lengths, anatomical joints percents, tissues percents, pH and mioglobin content) and also between sex in few determinations. Moreover, tables with correlations between variables are presented.