The purpose of this paper is to provide an overview of autonomic nervous system and gastrointestinal changes that occur during motion sickness. It is important to consider that motion sickness is a syndrome that can vary between individuals and within individuals and between and within motion sickness-inducing stimuli. Vomiting should be considered a discrete event of the motion sickness syndrome. Given so much variability in motion sickness symptoms, it should be expected that the physiological response to motion sickness will vary as well. This appears to be the case with the autonomic nervous system and gastrointestinal changes during motion sickness. Although much research remains to be done, it appears undeniable that the physiological expression of motion sickness is mediated by the autonomic nervous system, and when nausea is a predominant symptom, the stomach in general shuts down in a response characterized by decreased normal gastric myoelectrical activity and delayed gastric emptying.