To the Editor: In the May 2011 issue of the Journal, Carrie L. Dodrill et al. (1) cited epidemiological evidence that there are approximately 9,000 incident cases of prescription opioid abuse every day in the United States. This statistic cogently frames their discussion and the public health problems that surround this emerging epidemic. But if the authors are correct that there is minimal risk of developing opioid dependence in persons who have no history of substance abuse, 0.2% by the estimate provided, only 18 of the 9,000 new cases of opioid abuse would be individuals with no history of substance abuse. This would imply that it is unnecessary to assess any prognostic indicators other than the patient's substance abuse history. However, the authors' estimate seems implausibly low.