The aim of this study was to investigate the variables affecting headache occurrence in patients with multiple sclerosis (MS). Seventy-two MS patients with comorbid headaches completed a 28-item questionnaire. This evaluation assessed each patient's demographics, headache description and modifying factors, social history, and impact on quality of life. Our patients reported a wide spectrum of headache presentations, characteristics, and resulting disability. We discuss the patterns in our data in the context of current hypotheses regarding headache and MS causality. In our patients, migraines with aura strongly correlated with MS exacerbations, suggesting that they might be useful as a marker for flare-up onset. Patients' pain descriptions varied based on their headache frequency, history, and relationship to MS progression. Due to the severity of headache in MS patients and resulting impact on their activities of daily living, a thorough analysis of headache presentation is warranted in such patients. Int J MS Care. 2013;15:73-80.P eople with multiple sclerosis (MS) have an increased incidence of headaches, although the comorbidity of headaches and MS is poorly understood. 1 Lifetime prevalence appears to be highly variable, with reports ranging from 4% to 58%. [2][3][4][5][6][7] Despite the inconsistency of prevalence reporting, there is clinical value in the identification of headache incidence in MS patients. 2,8,9 Evidence suggests that headaches may vary based on MS form and lesion location, and MS patients with migraines have a more symptomatic clinical course of the disease. 8 In addition, screening patients with MS for headaches has treatment implications. Several medications used to treat MS have been shown to exacerbate headaches, leading to a decreased quality of life and possible treatment nonadherence. 8 Owing to the highly variable presentation of headaches in patients with MS, much remains to be elucidated about the variables affecting headache development. We analyzed a number of factors in relation to headache incidence in a sample of our patients with MS, focusing on headache history, pain description, modifying factors, social history, relation to disease progression, and impact on quality of life.