The Chilote sheep has been developed in an isolated environment, based on grazing lands with low nutritive value belonging to small-scale producers, because of which there is little information about the use of this breed for meat production. The objective of this work was to determine the effects on lamb carcasses of two breeds with different productive purposes and fed on pastures with different nutritional quality. Three groups of lambs were used. The first and second groups were composed of 13 and 11 Chilote lambs respectively, and the third composed of six Suffolk Down lambs. Lambs remained with their mothers, the first group on naturalized pasture and the rest on rangeland. Animals were slaughtered at 90 d of age. Live weight, carcass weight and yield, and several zoometric parameters were determined, as well as the weight of commercial cuts and the muscle, bone and fat ratios. Hide and hoof weights were also measured. For the effect of breed, Chilote lamb is narrower (P < 0.05) than Suffolk Down, but with a higher proportion of hide (P < 0.05) and hooves (P < 0.05). The type of pasture only affected hot carcass yield, which was higher in Chilote lamb with naturalized pasture than with rangeland (P < 0.05). There were no effects of breed or pasture type on the main characteristics of the lamb carcasses.