The high curve speed railway vehicles of the Japanese National Railways, the so called pendulum swing trains, have been running since 1973 with the aim of increasing speed on ordinary routes with a lot of curve track sections. The structure of high curve speed railway vehicles is designed to set up rollers between the body and the bogie, so as to be capable of running at higher speed at the curve sections, compared with that of older-type trains, by inclining the body when centrifugal force occurs. Although the aim of increased speed has been attained, it has been pointed out that the swing of the high curve speed railway vehicles is stronger than that of older-type trains. In this study, the author examined the motion sickness induced by the swing of these railway vehicles among both passengers and conductors with a selfadministrated questionnaire. The results are summarized as follows: 1) A higher percentage of passengers complaining of motion sickness and riding discomfort was observed in the high curve speed railway vehicles than in the control trains. The passengers pointed out the swing of the high curve speed vehicles most frequently as the reason for riding discomfort. 2) Conductors working on high curve speed railway vehicles complained of motion sickness symptoms at significantly higher rates on both outward and inward way than in the control trains. 3) Although more preventive measures against motion sickness were taken by conductors on high curve speed vehicles, they still suffered more from motion sickness and experienced more difficulties in the course of their work than those on the control trains. 4) It was considered that the difference between the rates of conductors and passengers complaining of motion sickness were due to the difference in responses to the riding on the train between the two groups. 5) Working on high curve speed railway vehicles brought conductors not only motion sickness but also subjective feeling of fatigue as well. Judging from these results, the high rate of subjective complaints of passengers and couductors riding on high curve speed railway vehicles resulted from the difference between the structure of these vehicles and that of older-type trains.