Many patients who suffer from orthostatic intolerance (OI) may also have severe fatigue and extreme exercise intolerance. In some of these patients, fatigue may be so severe that they are unable to maintain employment. In some, even the activities of the daily living may be compromised. We report on the use of modafinil in a subgroup of patients who failed therapy with commonly used medication for fatigue in patients with OI. The study was approved by the institutional review board. A retrospective nonrandomized analysis was preformed on 60 patients evaluated at our autonomic center for OI from 2003 to 2010. The diagnosis of OI was based on patient history, physical examination, and reponse to head up tilt table testing. All these patients had fatigue as their predominant symptom. Multiple trials of stimulants including methylphenidate, amphetamine, or dextroamphetamine failed to provide symptomatic relief of fatigue in these patients. Each patient received modafinil (100-200 mg daily). The mean follow-up period was 9 ± 3 months. A treatment was considered successful if it provided symptomatic relief from fatigue for the patient. Sixty patients, age 29 ± 15, 52 women were included in the analysis. Migraine (57%) and joint hypermobility syndrome (33%) were common comorbidities. Out of 60 patients, 40 patients reported initial improvement with initiation of modafinil therapy. Twenty patients reported no change in their symptoms of fatigue. Of the 40 patients who showed initial improvement in their symptoms 4 had eventual recurrence of fatigue after 3 months of modafinil therapy. Thirty-six patients continued to demonstrate symptom relief from fatigue for more than 6 months. In a selective group of patients of OI, modafinil may improve fatigue.