The aim of this study was to determine the relative prevalence and clinical characteristics of patients with pure menstrual migraine (PMM) and menstrually related migraine (MRM), and to compare them with the women free of it in an outpatient clinic-based population. Adult menstruating women with ICHD-2 migraine were included. Demographic data were obtained by verbal report. Study women were asked to keep a headache diary for 6 months, in which they recorded information on headache characteristics, medication use and presence of menses. Iron deficiency anemia was considered to be present if the patient had received therapy for iron deficiency anemia or laboratory tests indicated low iron and/or hemoglobin levels (within one year). A total of 289 women were included, 52 (18.0%) with PMM and 116 (40.1%) with MRM, whereas 121 (41.9%) women had not observed any relationship between migraine and their menstrual cycle (non-MM). Duration of migraine attacks was longer in PMM/MRM patients (P < 0.0001). No significant difference was observed according to other migraine-associated symptoms. Women with PMM/ MRM took significantly more tryptans (P < 0.0001) and iron deficiency anemia was significantly more common in women with PMM/MRM (P = 0.008). In conclusion, this study supported earlier findings that PMM/MRM has similar clinical characteristics as non-MM, except for longer duration. In addition, iron deficiency anemia is more common in women with PMM/MRM, which may be an underlying mechanism aggravating migraine attacks.