Part 1 describes a developmental study to identify an optimum Dial Test procedure and the results of using the procedure on three groups with differing aviation experience. The problem was to determine that combination of rotational velocity of a slow rotation room, time between dial settings, and number of sequences to be performed which would yield the best measure of susceptibility to motion sickness. Parts 2 and 3 report the correlations between Dial Test scores and the Modified Romberg and the Coriolis illusion, and with scores from a Motion Sickness Questionnaire. Modified Romberg scores had a small but significant relationship with Dial Test scores for the 'incoming flight student' group, and this relationship was almost significant for the 'proficiency billet aviator' group. Coriolis illusion scores were not significantly related to Dial Test scores but were in the predicted direction. Statistically significant relationships were obtained between Dial Test score and scores from two keys to the Motion Sickness Questionnaire; these need cross- validation, however.