Several studies have examined the occurrence of eating disorders in athletes. However, little has been written about the frequency and phenomenology of compulsive exercising in eating disorder (ED) patients. Given this, we studied a series of 110 patients who presented to the Medical University of South Carolina Eating Disorders Program and met lifetime DSM-III-R criteria for bulimia nervosa (n = 71), anorexia nervosa (n = 18), or both disorders (n = 21). All patients completed the Diagnostic Survey of the Eating Disorders (DSED), a self-report measure of demographic and clinical characteristics including time spent exercising daily. Thirty-one (28%) of the 100 patients reported that they exercised > or = 60 min every day (M +/- SD = 105 +/- 48 min) and were defined as compulsive exercisers (CEs). In addition, 3 CE patients with a DSM-III-R diagnosis of eating disorder not otherwise specified (EDNOS) were included for comparison with non-CEs on a number of variables. CEs had significantly greater ratings of body dissatisfaction (p < .01) than non-CEs. Non- CEs were significantly more likely than CEs to vomit and use laxatives (p < .01, chi 2), and they had a higher frequency of binge eating ( p < .006, Kruskal-Wallis). There was a trend for a significantly higher frequency of compulsive exercising in the patients with anorexia nervosa (38.5%) than those with bulimia nervosa (22.5%) (p < or = .06, chi 2).