We conducted a population-based study of consanguineous marriages in Jordan. About two thousand households were interviewed. First cousin marriages were encountered in 32.03%, second cousin in 6.8%, distant relation in 10.5%, and no relation in 50% of all marriages, respectively. Inbreeding coefficients were compared with those of other countries. The most important variables affecting inbreeding were social tradition, religion, education, and place of residence--urban vs. rural. Secular trends appear rather stable since the early decades of the twentieth century, especially for first cousin marriages. Jordan society showed a deeply rooted traditional behavioral pattern when inbreeding is considered.