Blood specimens were collected from 184 Kurds living in those parts of northwest Iran from which many of the Kurdish Jews, tested in Israel, or their parents, came. Tests were done for the antigens of 10 blood group systems, for the genetic variants of six systems of plasma proteins, and of nine systems of red cell enzymes, and for abnormal haemoglobins. The gene frequencies calculated from the results do not differ greatly from those found in neighbouring populations. They also show a general resemblance to those of the Kurdish Jews, except that the latter have a very much higher incidence of glucose 6-phosphate dehydrogenase deficiency. The possible reasons for this marked difference affecting one genetic system only, are discussed.