Objectives. When open reduction and internal fixation is indicated for the management of mandibular fractures, it is generally agreed that nonrigid fixation and rigid fixation represent acceptable treatment alternatives. Opinions vary, however, regarding the cost-effectiveness of the two alternatives. The purpose of this study was to compare the costs of these treatments of mandibular fractures that required open reduction and internal fixation. Study design. Cost-effectiveness analysis was used to determine the most efficient resource used to treat mandibular fractures requiring open reduction and internal fixation. Cost-effectiveness was defined as the treatment charges per successfully treated patient. Data were collected retrospectively from patients with mandibular fractures treated between 1991 and 1994. The patient's medical record and hospital billing record were used as data sources. To estimate treatment charges, the sample was divided into three groups: (1) group 1, patients treated with nonrigid fixation without postoperative complications, (2) group 2, patients treated with rigid fixation without postoperative complications, and (3) group 3, patients treated with either procedure who had postoperative complications. The study variables were grouped into two categories: clinical information and charges. Treatment charges for both treatments were estimated and compared. Results. Data were collected for 12 patients in group 1 and 11 patients in group 2. Costs for rigid fixation averaged $1,468 more per patient than for nonrigid fixation in uncomplicated cases. There were 11 patients in group 3. The average cost to treat a postoperative complication was $11,637. Given the institution-specific treatment cost and the probability of complications, rigid fixation was a more cost-effective treatment than nonrigid fixation. Conclusion. Cost estimates for treating mandibular fractures may vary widely depending on practice patterns and complication rates. Despite these cost variations, one may determine the most cost-effective treatment alternative by estimating treatment costs of both uncomplicated and complicated cases and the postoperative complication rate.