Twenty-nine children of brother-sister or father-daughter matings were studied. Twenty-one were ascertained because of the history of incest, eight because of signs or symptoms in the child. In the first group of 21 children, 12 had abnormalities, which were severe in nine (43%). In one of these the disorder was autosomal recessive. All eight of the group referred with signs or symptoms had abnormalities, three from recessive disorders. The high empiric risk for severe problems in the children of such close consanguineous matings should be borne in mind, as most of these infants are relinquished for adoption.