This study used electronic thermography, an alternative diagnostic imaging modality, to assess the thermal image characteristics of the normal TMJ in 30 asymptomatic subjects. Assessments made included: thermal pattern recognition and symmetry, absolute temperature measurements and differences in absolute temperature measurements, and mean temperature measurements and differences in five anatomic zones. Results indicated the presence of a common thermal TMJ pattern in two thirds of patients, with variations from this pattern in the remaining patients. All TMJ thermal patterns demonstrated marked thermal symmetry, with delta T 0.2 degrees C in the region of the TMJ and related regions of the face. This consistent symmetry demonstrated in normal subjects suggests that substantial thermal asymmetry may prove to be a reliable indicator of TMJ disease.