Fourteen families in which more than one child was diagnosed with hydrocephalus of prenatal onset were seen in our genetic counseling clinic. In 7 families only males were affected: in 2 X-linked hydrocephalus was diagnosed while X-linked inheritance was suspected in 3 other families. These 5 families were of Jewish origin. In the 8 families of Arab origin, the parents of the affected children were consanguineous. In 6 of these families at least one female was affected and the hydrocephalus was most probably inherited as an autosomal recessive trait. This type of hydrocephalus of prenatal onset appears to be frequent among Palestinian Arabs.