The study carried out at Dort Mevsim Meat Integrated Facility in Susurluk district, Balikesir province, Turkey. In each genotype, there were 20 male lambs. Suffolk and German Mutton Merino lambs were subjected to fattening for 70 days. At the end of the trial, 6 male lambs from each genotype were slaughtered. Slaughter weight, ADG, concentrate feed efficiency, hot carcass weight, chilling carcass weight, hot dressing percentage and chilling dressing percentage were 43.9 kg, 301 g, 3.44 kg, 23.18 kg, 22.24 kg, 52.80 % and 50.66 % in Suffolk lambs; these values were 43.1 kg, 296 g, 3.86 kg, 21.85 kg, 20.89 kg, 50.70 % and 48.47 % in German Mutton Merino lambs, respectively. Hot and chilling carcass weights of Suffolk and German Mutton Merino lambs were significantly different (P<0.05). The findings of the current study showed that Suffolk lambs tended to have higher hot and chilling carcass weights, although there were no statistical differences between the two genotypes in terms of slaughter weights, average daily weight gains and other slaughter traits. These results also indicate that the carcasses for retail sale from the Suffolk lambs were more in quantity when compared to German Mutton Merino lambs.