These proposals formed the basis for the experimental work of the thesis, which investigated three possible associations of sympathetic nervous system activity with individual motion sickness susceptibility: sympathetic activity at rest, initial reactivity to a motion stimulus, and the onset time of activation during motion exposure. Four laboratory experiments have been conducted. The first involved techniques for acquiring and processing physiological data. The second experiment investigated the possible associations of sympathetic nervous system activity during resting conditions with subsequent motion sickness susceptibility. The third experiment investigated the possible association of sympathetic nervous system reactivity, during the first four minutes of motion exposure, with ensuing motion sickness susceptibility. The results showed no significant correlation of sympathetic reactivity with eventual motion sickness susceptibility. However, the results indicated that individuals may vary in the onset time of changes in sympathetic activity following the start of the stimulus. The results also indicated that physiological measures acquired during motion exposure may only change significantly from resting conditions when subjects experience nausea. The fourth experiment investigated the temporal development of motion sickness symptoms. These included symptoms related to the activation of the sympathetic nervous system, disruption to gastric activity and the perception of nausea. In most subjects, sympathetic symptoms occurred before symptoms of gastric disruption, which occurred before reports of nausea (p < 0.05). However, eight out of twenty six nauseous subjects reported nausea before symptoms of sympathetic activation or gastric disruption. The experimental work of this thesis indicates that individual differences in sympathetic nervous system activity are not factors influencing motion sickness susceptibility. Some individuals who are highly susceptible to motion sickness develop nausea before activation of the sympathetic nervous system or gastric disruption. A descriptive model of motion sickness symptom development has been evolved from the experimental work and the literature review of the thesis. Physiological measures of motion sickness have been developed in this thesis and their validity investigated.