A sample of 119 pairs of twins, together with their 87 siblings and 100 pairs of parents, were examined with respect to susceptibility to the motion sickness syndrome. Children were found to exhibit resistance to the syndrome below two years of age, and females were more susceptible than males. The incidence appeared to be highest in families with both parents affected. Concordance rates were much higher in MZ (100%) than in DZ pairs (27.6%). Genetic effects are likely, but cultural factors should not be ignored.
