The preliminary findings of three investigations of separate occurrences of industrial mass psychogenic illness are presented to provide information on the characteristics and nature of mass psychogenic illness and to indicate some of the similarities in the incidents. The majority of employees were female and the symptoms were primarily subjective somatic complaints, including headaches, nausea, and chills. The actual outbreak of complaints was usually triggered by a physical stimulus, such as an odor, which was believed by the workers to be the source of the discomfort. The affected workers were found to have more discomfort from physical and psychological stressors (work pace, poor lighting, noise, role ambiguity, boredom). It is suggested that peer and supervisory relations are important as potential precipitators of mass psychogenic illness in an industrial setting.