Recently, several studies have indicated the rate of consanguinity ranging between 20 and 70% in the Middle East. Turkey is one of the countries with a high rate of consanguineous unions in the Middle East. In this study, the rate of consanguinity and its effects on spontaneous abortus, stillbirth, infant mortality, and birth defects were investigated in a population sample residing in Kahramanmaras city, Turkey.For this study, 1000 randomly selected women, aboriginals of Kahramanmaras city, Turkey, were interviewed at their home and the concerning information was obtained by administration of a questionnaire between April 2002 and March 2003.The prevalence of consanguinity was found to be 30.6% with the mean inbreeding coefficient of 0.015373. The most common type of consanguineous mating was first cousin marriages with the frequency of 22.6%. The family pressure and love were the main reasons for marrying with a relative. The mean age at marriage of women and men were lower in consanguineous marriages than that of non-consanguineous unions. There was a negative correlation between the consanguinity and educational level of both sexes. The results revealed differences between consanguineous and non-consanguineous matings, in terms of stillbirth, infant mortality and birth defects whereas the rate of spontaneous abortus was found to be the same in 2 kinds of marriages.The incidence of consanguinity and of first cousin marriages is found to be very high in the Kahramanmaras city. A reduction of consanguinity rate is necessary for the health quality of the population.