A rotating optokinetic drum was used in three laboratory studies to test the hypothesis that Asian subjects are hypersusceptible to motion sickness. The results of the first study showed that Chinese women compared to European-American and African-American women experienced significantly more severe symptoms of motion sickness and greater disturbance of normal gastric myoelectric activity. A second study yielded similar results using American-born children of Asian parents. The results of a third study using Chinese men and women were similar and showed a significant increase in vasopressin during rotation. Possible genetic mechanisms that may account for these results are discussed.