The purpose of this research was to determine of optimum slaughter weights of Karacabey Brown bull. Twenty Karacabey Brown bull, aged 6 - 8 months, were allocated into three groups and each group consisted of 7, 6 and 7 animals. Initial average Live – weights of animals in each group were 197.6, 212.0 and 227.9 kg. Each group of animals were kept and managed in semi - open barn with a small yard (Loose housing} and given a pelleted concentrate diet (Crude Protein 13.83 %) and hay (CP 5.14 %) throughout the experimental period. Each group of animals were slaughtered at 400, 450 and 500 kg. Live - weight. Average fattening periods in the groups were 170.8, 197.6 and 230.7 days; and average daily Live - weight gains were 1207, 1225 and 1207 grams. Feed intakes (Concentrate+ hay) were 7.19, 7.69 and 8.26 kg/kg gain. Animals slaughtered at 500 kg. had greater dressing percentage (57.7 %), more first quality cuts and Less bone (15.5 %). It is concluded that 500 kg. Live - weight is suitable for slaughtering of Karacabey Brown bulls