To evaluate the diagnostic accuracy of clinical signs and symptoms of mandibular fracture, a prospective study of emergency department patients presenting with mandibular trauma was undertaken. Patients with airway compromise, who were edentulous, or could not cooperate with the physical examination were excluded. Over a 1-year period, 119 patients were studied. The presence of malocclusion, trismus, facial asymmetry, or a positive result on the tongue blade test (inability to grasp and hold a tongue blade between the teeth) was significantly associated with a mandibular fracture. Malocclusion and facial asymmetry were strong predictors of fracture, and a negative result on the tongue blade test was a strong predictor of nonfracture.