Objective:To develop a mathematical model that simulates whether or not to extract teeth in optimizing orthodontic treatment outcome and to formulate the morphologic traits sensitive to optimizing the tooth-extraction/nonextraction decisions. Materials and Methods: A total of 188 conventional orthodontic records of patients with good treatment outcomes were collected, and dentofacial morphologic traits, along with their degrees of influence in the optimized model, were determined. Results: The rate of coincidence between the recommendations given by the optimized model and the actual treatments performed was found to be 90.4%. The major morphologic traits and their corresponding influences in improving the simulation accuracy of the model were the incisor overjet (3.0) and the size of the basal arch relative to the sum of the mesiodistal crown diameters of the upper dentition (2.4) and the lower dentition (2.0). The remaining 22 morphologic-trait variables were also found to be indispensable in achieving robust simulation readings. Conclusion: A mathematical model that simulates whether or not to extract teeth in optimizing orthodontic treatment outcomes with a success rate of 90.4% at its prediction performance was developed. This model has 25 morphologic traits with four major categories (sagittal dentoskeletal and soft tissue relationship, vertical dentoskeletal relationship, transverse dental relationship, and intra-arch conditions) that affected the accuracy in determining optimal tooth extractions/nonextractions. (Angle Orthod. 2009;79:885-891.)