Purpose Orthorexia nervosa, or pathological dieting based on being "healthy," has been of growing interest. Clinical data are limited to less than a half-dozen case studies reporting instances of medical problems due to healthful eating. However, more than a dozen studies using a measure to identify orthorexia, the ORTO-15, report very high prevalence rates in non-clinical samples. Point prevalence rates are reported from 6 % to nearly 90 %. Such variability could be due to cultural issues or psychometric problems with the instrument. This study examines prevalence rate of orthorexia in a US sample. Method The ORTO-15 was administered to 275 US college students along with other questions regarding diet, exercise, and health. Results While the ORTO-15 indicated a prevalence rate of 71 %, only 20 % of the sample endorsed a dietary practice of removing a particular food type (e.g. meat) from their diet. Those who endorsed following a vegan diet had the highest (less pathological) mean ORTO-15 score. Further, when classifying participants based on their seriousness about healthy eating and whether their diet had led to impairment in everyday activities and medical problems, less than 1 % of the sample fell into such a category. Conclusion As in other countries, a large proportion of a non-clinical US sample scored in the orthorexia range on the ORTO-15. However, this instrument is likely unable to distinguish between healthy eating and pathologically healthful eating. Our estimate is that orthorexia nervosa like anorexia nervosa and bulimia nervosa, is not a common condition.