The article introduces a new statistical potential called Discrete Optimized Protein Energy (DOPE) for assessing and predicting protein structures. DOPE is derived from probability theory and does not rely on adjustable parameters, making it more accurate and reliable compared to other scoring functions. The authors derive DOPE from a sample of native protein structures, treating the reference state as a finite sphere with uniform density and appropriate size, which is a significant improvement over previous methods. They test DOPE against five other scoring functions using multiple target decoy sets and find that DOPE outperforms them in terms of native state detection, score-error correlation, and identification of the most accurate non-native model. The study highlights the importance of a rigorous treatment of the reference state in statistical potentials and demonstrates the practical utility of DOPE in various applications, such as model assessment, loop modeling, and fitting into cryo-electron microscopy mass density maps.The article introduces a new statistical potential called Discrete Optimized Protein Energy (DOPE) for assessing and predicting protein structures. DOPE is derived from probability theory and does not rely on adjustable parameters, making it more accurate and reliable compared to other scoring functions. The authors derive DOPE from a sample of native protein structures, treating the reference state as a finite sphere with uniform density and appropriate size, which is a significant improvement over previous methods. They test DOPE against five other scoring functions using multiple target decoy sets and find that DOPE outperforms them in terms of native state detection, score-error correlation, and identification of the most accurate non-native model. The study highlights the importance of a rigorous treatment of the reference state in statistical potentials and demonstrates the practical utility of DOPE in various applications, such as model assessment, loop modeling, and fitting into cryo-electron microscopy mass density maps.