Positional cloning is occasionally facilitated by the identification of a chromosomal aberration. We are studying a Turkish family, first described by Bilginturan et al., who have a monogenic form of hypertension, and we have reason to believe that a chromosomal aberration in a Japanese child may facilitate our cloning of the responsible gene. The hypertension gene in our family is unique in that it causes, by as yet undefined mechanisms, increased peripheral vascular resistance. Pedigree analysis of the Turkish kindred allowed us to map the gene to 12p11-p12. The kindred has a second trait, brachyclactyly, which cosegregates with the hypertension. The brachyclactyly, which involves both hands and feet, features shortened metacarpals and phalanges, as well as cone-shaped epiphyses. 11 refs., 2 figs.