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The first large scale study of migraine epidemiology from a nationwide collaborative group was carried out in 22 Chinese rural and ethnic minority communities of 21 provinces of the People's Republic of China during 1985 in a well-defined population of 246,812 inhabitants. On the day for which prevalence was calculated, January 1, 1985, there were 1703 cases of migraine, yielding a point prevalence ratio of 690/100,000. The prevalence ratio of migraine for females was higher than that for males. The overall sex difference in the prevalence ratio was significant (Z=26.57, P<0.0001), The prevalence began from the age before 10 years old, and monotonically increased until it had reached its peak at age 40–49, then decreased steadily. The geographic distribution of the prevalence has the tendency that the south is higher than the north, and the west is higher than the east. The incidence rate of new cases was 37/100,000 in 1984. The incidence rate reached its peak at age 15–19, then gradually decreased. Incidence before age 10 and after age 50 was rare. The incidence rate of migraine was higher in females than in males. Sex difference in the incidence rate was significant (Z=4.35, P<.0001}. Clinical Manifestations: In 804 cases with auras, 793 (46.56%) had visual disturbances, 11 (0.64°/o) had hemiparesis or hemiparesthesia. Concomitant nausea or vomiting occurred in 1,349 cases (79.21%). Among those 1703 cases with headache, 584 cases (34.29%) were unilateral, 791 cases (40.45%) were bilateral and 328 cases (19.26%) were uncertain. In duration of headache, 744 cases (43.69%) had less then 24 hours and 720 cases (42.28%) had 24 hours or longer. In the frequency of episodes, 818 cases (48.03%) had no more than once per month and 742 cases (43.57%) had more than once per month. Classification: There were 752 cases (44.16%) of prodromal type (classical) migraine, 929 cases (54.55%) of non-prodromal type (common) migraine, 14 cases (0,82%) of cluster headache, 2 cases (0.12%} of hemiplegic migraine. Each of vertebrobasilar and ophthalmoplegic types had 3 cases (0.18%), Trigger Factors for Episodes: 678 cases (39.81%) were triggered by mental stress (tension, anxiety etc.), 509 cases (29.81%) by change of weather and 293 cases (20.88%) of females by menstruation.