Preventive treatment is an important part of migraine therapy. When prescribing medication, physicians should understand patients' treatment preferences and select drugs that most closely meet their patients' needs. Understanding the factors that influence patients' preference increases physicians' ability to select appropriate migraine therapy. However, unlike acute migraine treatment, patients' preferences for migraine preventive treatment have never been studied. We enrolled 250 patients who attended the Jefferson Headache Center and Sao Paulo Headache Center and had a primary headache diagnosis. Patients' age, gender, body mass index (BMI), headache diagnosis, headache frequency, duration, and intensity, headache disability (by MIDAS), and current preventive treatments were ascertained. Patients were asked to rate 7 aspects of headache prevention (efficacy, speed of onset, out-of-pocket expenses, adverse events, formulation of therapy, type of treatment, and frequency of dosing) in order of importance (1-7). Each patient also evaluated 12 different clinical scenarios, each one containing a simulation of 2 hypothetical headache preventive treatments, wherein patients could choose Product A, Product B, or neither. Patients were informed of each product's efficacy data (50%, 75%, or 100% headache elimination), adverse event profile (weight gain, concentration difficulty, and/or fatigue), and dosing frequency (once every 3 months, once per day, or twice per day). Most patients were Caucasian. Mean BMI was 26.55 +/- 5.34, range (17-45). Mean history of headache was 20.93 years. Fifty patients (40%) had 45 or more headache days in the past 3 months. Mean headache intensity score (0-10 scale) was 5.7 +/- 1.8. Patients were on various preventive treatments, including beta-blockers (48 [41%]), calcium-channel blockers (19 [16%]), antidepressants (52 [44%]), antiepileptics (46 [39%]), neurotoxins (16 [14%]), vitamins/herbal therapies (28 [24%]), and nonmedicinal therapy (38 [32%]). Of the 7 aspects of migraine prevention that patients were asked to rate, 72% rated effectiveness the most important aspect. Twelve percent rated speed of onset most important, 6% rated absence of adverse events most important, 3% rated formulation of therapy most important, 3% rated out-of-pocket expenses most important, and 2% rated type of treatment (prescription/vitamin) most important. None rated frequency of dosing as the most important factor. In the area of preventive treatment scenarios, patients were more likely to choose treatments with higher efficacy rates, fewer adverse events and less frequent dosing schedule. Patients indicated that they preferred the treatment options with higher efficacy rates even if side effects were present and a more frequent dosing schedule was necessary. Patients' preference regarding migraine prevention is very important in headache management. Patients rated efficacy the most important aspect in preventive therapy and preferred treatment options with higher efficacy rates. Future studies are needed for a better understanding of patients' preference for migraine prevention.