RESUMEN
Consanguineous marriage is an important type of marriage in the world including Iran. Familial marriage mean's marriage between a man and woman who has at least one common grandfather. The aim of this study was to determine the frequency of consanguineous marriage and some related factors in Tehran [2008]. This study was a cross-sectional with descriptive and analytic features. 180 couples who intend to marriage and come to health care centers of Tehran's [summer 2008] medical universities were randomly assessed with an author's built questionnaire. Means age of persons with consanguineous marriage and non-consanguineous marriage were 24.7 + 4.2 years and 25.6 +/- 4 years, respectively. The level of knowledge of majority of persons about the effects of consanguineous marriage was intermediate and lower. Most of people believed that genetic consult is very necessary. Frequency of consanguineous marriage was 17.7%. Incidence of familial marriage has no significant relationship with age, sex and education of persons [P>0.05], but there was significant relationship between occurrence of familial marriage and history of this type of marriage in their parent, family and friends [P<0.002]. Although the majority of persons in this study has not a proper level of knowledge about the effects of consanguineous marriage and thus need genetic consult, but their friends were the most important reference of their information about familial marriage and it's consequences. This reveals that communications and genetic consulters have a weak role in giving information to people