With the aim to study the effects of dietary energy and the slaughter weight on the carcass yield and characteristics of Pelibuey male lambs, the regional structure and tissue composition of 32 half carcasses, as well as the deposition pattern of visceral fat and its unsaturated fatty acid degree was assessed. The animals were fed two diets containing the same amount of crude protein (14.1%), but different energy density, diet I (D-I): 2.60 and diet II (D-II): 2.85 Mcal ME/kg DM. Lambs were slaughtered at 30, 37, 44 and 51 kg body weight. The data were analyzed on a completely randomized design with a factorial 2 × 4 arrangement. The commercial yield (%) differed (P ¿ 0.05) between diets (DI: 46.2 and D-II: 49.3) and between slaughter weights, increasing as the body weight increased. Neither diet nor the slaughter weight affected the carcass cuts; the piece that represented the highest percentage was the thorax (32.3%), followed by the leg (31.2%), shoulder (17.6%), abdomen (12.3%) and neck (6.7%). The D-II resulted in greater proportion of muscle (65.9%) than the DI (64.7%): as the slaughter weight increased so the fat did at the expense of bone and muscle. The energy density of the diet led to differences (P ¿ 0.05) in the amount of visceral fat (D-I: 5.8 ± 0.7 and D-II 7.0 ± 0.8), in the degree of unsaturated fatty acids (D-I: 39.2 ± 2.6 and D-II: 44.9 ± 2.8) and its deposition pattern (D-I: 51.7 ± 0.9; 48.3 ± 0.6 and D-II: 46.7 ± 0.6; 53.3 ± 0.8, respective percentages to carcass and viscera).