Abstract: In the genealogical investigation into 1210 patients with alopecia areata(AA),we found 75 cases with a positive family history of AA,the familial incidence was 6.2%.The incidence of AA in the 75 families (1093 cases) was 14.91% (163 cases).In these families,there were 142 patients in first-grade relatives of the family members,17 in second-grade,and 4 in third-grade.We observed 70 cases in 33 families within one generation,87 cases in 40 families within two succesive generations,and 6 cases in 2 families within three successive generations,four pairs of monozygotic twins appeared in this investigation,but just one of each pair was affected.The relationship between pathogenesis of AA and genetic factor has been discussed.

Key words: Alopecia areata, Familial Incidence