The American Dental Association has approved several devices as aids in the diagnosis of temporomandibular disorders. Concerns remain, however, about their safety and effectiveness. This article reviews the validity and use of several instruments that claim to serve as aids in the detection of masticatory muscle pain, trismus, joint noises, and limitation of jaw motion. A review of data from 62 published articles indicated that, although commercial devices that measure jaw muscle tenderness, muscle activity levels, joint noises, and jaw motion are safe and can document these phenomena, cost-benefit analyses of these devices have not yet been conducted. Moreover, these devices have not been shown to have stand-alone diagnostic value and, when tested, they have demonstrated unacceptable sensitivity and specificity levels. None of the instruments reviewed in this article can be said to provide more than ancillary documentation.