Information on trigger factors provoking a migraine attack, was collected in 217 migraineurs (176 women, 41 men). In this selected group of patients, most patients were spontaneously aware of one or more trigger factors; 184 (85%) of the patients reported trigger factors with a median number of 3 different trigger factors. The main trigger factors were menstruation (48%) or ovulation (8.5%) in women, certain food (44.7%), alcoholic beverages (51.6%) and stress 148.8%). After excluding the menstrual cycle as a trigger factor, trigger factors were more frequent in women, in older patients and in patients with a longer duration of disease. Women with a menstrual cycle-related migraine reported more trigger factors, other than the menstrual cycle itself, than women in whom the menstrual cycle had no influence on this migraine: this was especially so for food and beverages. The number and type of trigger factors in the women in whom the migraine was not menstrual cycle-related, were fully comparable with those in men. Patients in whom alcohol acts as a trigger factor had also significantly more other trigger factors, especially food. The same holds true for patients reporting stress as a trigger factor, but the latter difference is not significant when the different subgroups of trigger factors (food, beverages, other)are considered. Certain trigger factors may be mutually related.