Forty male lambs of the mountain Greek breed were used to evaluate the effect of age at slaughter on carcass characteristics and composition. The slaughter of lambs was carried out at the age of 30, 45, 60, 75 and 90 days. The slaughter procedure, carcass dissection and carcass composition were realized according to the standard method of CIHEAM-AGRIMED programme. The results of this work showed that the lambs of different age groups did not differ in dressing percentage significantly. The proportion of muscles showed a tendency of increase with the increasing slaughter age but the differences were not significant. The proportion of total fat in carcass increased with the increasing slaughter age from 20.84 to 23.59% for the age group of 30 and 90 days, respectively (P < 0.05). On the contrary, as the age at slaughter increased, the proportion of bones decreased (P < 0.05). Subcutaneous, intermuscular, perinephric and pelvic fats increased with the slaughter age, but only the subcutaneous fat was influenced significantly (P < 0.05). Among the different commercial cuts proportions of long leg, first 5 ribs and shoulder decreased, while those of last 8 ribs-loin and breast-flank increased (P < 0.05). The overall results suggest that the slaughter age of lambs of the mountain Greek breed should be increased from the present ~45 days to more advanced age of 75 or 90 days in order to improve the farmers' profits without serious negative effects on the quality of carcasses or meat of lambs.