This research was conducted to replicate and expanded the work of Bodfish et al. [Bodfish, J. W., Harper, V. N., Deacon, J. R., & Symons, F. J. (2001, May). "Identifying and measuring pain in persons with developmental disabilities: A manual for the Pain and Discomfort Scale (PADS)." Western Carolina Center Research Reports] by assessing the functional sensitivity of the Pain and Discomfort Scale (PADS) in patients with MR. We used the PADS to detect pain and discomfort during a dental scaling and polishing procedure. Subjects (N=28) with cognitive and communication deficits were assessed at multiple baselines, during and after the procedure. The results indicated that scores on the PADS were significantly higher during the scaling procedure than during all other observations quantified by the PADS. We conclude that the PADS is a functionally sensitive measure that may lack specificity, but that may also represent the state of the psychometric art of assessing pain in patients who have MR.