Abstract
Using the data on the incidence of primary varicose veins among first-order relatives of 830 affected and 402 non-affected subjects, estimates of segregation ratios with respect to parental mating types were derived on the basis of the incidence of the condition in parents, on the one hand, and among sibs of probands on the other hand. The segregation ratio clearly depends on the parental mating type and seems higher if the mother is affected than if it is the father, though the difference is not significant. Assuming the hypothesis of polygenic inheritance it was possible to obtain estimates of the heritability of the condition. This amounts to about 50% and is slightly higher for males than for females. The limitations of the methods employed and the results obtained are discussed.