The purpose of this investigation is to compare the prevalence of internal derangement of the temporomandibular joints (TMJ) in asymptomatic volunteers versus symptomatic subjects using magnetic resonance imaging (MRI), with a detailed comparison to clinical signs and symptoms and with attention to a prior history of orthodontic treatment. Bilateral MRI scans were obtained of the TMJs in 76 asymptomatic volunteers and 102 symptomatic patients. A comparison was made to the clinical signs and symptoms, a history of orthodontic treatment, and to the MR findings. The MRI scans were reviewed using established criteria for disk displacement and the reviewers were blinded as to the clinical information. Our results show a prevalence of disk displacement in 25 of 76 (33%) volunteers and 79 of 102 (77%) patients with a statistically significant difference (p < 0.001). No statistical link was noted between a history of prior orthodontic treatment and internal derangement of the TMJ.