In this study, the prevalence of substance use disorders among 100 patients with chronic fatigue was examined. 28 patients met DSM-III-R criteria for a lifetime diagnosis of substance abuse or dependence; 10 of these patients had a current diagnosis. Patients with chronic fatigue who had a lifetime history of a substance use disorder reported more lifetime depressive symptoms & were more likely to have had suicidal ideation or attempts. (20 refs.)