This systematic review examines evidence evaluating whether women with headaches who use combined oral contraceptives (COCs) have a greater risk of stroke than women with headaches who do not use COCs. We searched MEDLINE for articles published from 1966 through March 2005 relevant to headaches and COC use as risk factors for stroke. Of the 79 articles identified, nine met our selection criteria (eight reports of six observational studies plus one meta-analysis). All studies reported specifically on migraine headaches. Evidence from six case-control studies suggested that COC users with a history of migraine were two to four times as likely to have an ischemic stroke as nonusers with a history of migraine. The odds ratios for ischemic stroke ranged from 6 to almost 14 for COC users with migraine compared with nonusers without migraine. The three studies that provided evidence on hemorrhagic stroke reported low or no risk associated with migraine or with COC use.