Results of this study indicate that correlations between real-time ultrasound loin depth and carcass loin muscle area and between carcass loin depth and carcass loin muscle area are high. However, using carcass loin muscle area as the true value, the standard error of prediction for real-time ultrasound loin muscle area was lower than those for loin muscle areas predicted from either real-time ultrasound loin depth or carcass loin depth. Real-time ultrasound and carcass depth or length or a combination thereof is a less accurate predictor of carcass loin muscle area than simply real-time ultrasound loin muscle area alone.