The purpose of our study was to prospectively evaluate the impact of preventive drug treatment on the quality of life of patients with episodic migraine (EM). Quality of life evaluations can enhance traditional measures of therapeutic efficacy. Thirty-five consecutive EM without aura patients attending a tertiary care unit (Batatais Headache Clinic) entered the study. They were given a prescription for preventive medication and completed the validated Portuguese version of the generic instrument Short Form-36 (SF-36) questionnaire. Six months later, patients were given another SF-36. We compared the pre-treatment and post-treatment scores for the SF-36 and analysed the headache diaries. The mean age of the 35 patients (32 women and 3 men) was 40.2 years (range 18-60 years). All 35 patients completed the pretreatment and follow-up SF-36. The pre-treatment and post-treatment mean frequency of migraine attacks was 9.16 and 2.4 crises per month, respectively (p<0.05). After the six months of preventive treatment, six of the eight domains evaluated by the SF-36 (role physical, bodily pain, general health, vitality, social function and mental health) showed statistically significant (p<0.05) improvement. The preventive treatment of migraine leads to a significant improvement in the quality of life of patients with EM. This improvement was measurable by the general quality of life instrument SF-36.