Three data sets were compiled to determine the relationship of weight, performance, hip height and ultrasound-measured fat thickness to hot carcass weight and fat thickness. Weight is generally the best predictor of relative differences in carcass weight at any time in the production system. Hip heights do not predict relative differences in carcass weight. Although the combination of hip height and weight is a more precise indicator of carcass weight than is hip height alone, generally this combination is inferior to weight alone. Only ultrasound-measured fat thickness predicted relative differences in fat thickness. Prediction of relative differences in carcass weight from body weight and fat thickness from ultrasound scans improved as marketing date approached