OBJECTIVE: This study aimed to determine the diagnostic value of ultrasonography (US) in internal derangements of temporomandibular joint (TMJ) and to compare its efficacy with magnetic resonance imaging (MRI). METHODS: Fifty patients with MRI indications due to a TMJ disorder were enrolled. Findings of the clinical examination, US examination and MRI examination were noted by seperate clinicians and the sensitivity, specificity and diagnostic accuracies of all examinations were compared. RESULTS: When compared with MRI, the sensitivity, specificity and diagnostic accuracy of the clinical examination for the internal derangements were 73%, 37%, and 70%, respectively and 75.7%, 33.3% and 73.0% for US examination, respectively. CONCLUSION: US can be considered as an alternative to MRI as it can be used to detect the disc position, internal derangements, intraarticular fluid accumulations and superficial condyle changes with minimally better results than clinical examination.