The effect of shift work on workers in the food processing industry was studied. Approximately 1000 food processing workers (273 day, 269 afternoon, 267 night, and 200 rotating shift workers) representing eight facilities, were administered psychological questionnaire surveys, and employee health records were reviewed. Cases of work related injury and disease as well as sick absences were recorded. Night shift workers averaged the least amount of sleep per 24 hours (6.4 hours), while afternoon workers reported the most sleep per 24 hours (7.4). Night and rotating shift workers reported the most sleep related difficulties. Afternoon shift workers reported more incidences of depression, anger and confusion than did night shift or day workers. Male night shift workers reported the highest frequency of gastrointestinal problems, while male day workers indicated a greater frequency of arthritis and high blood pressure than the male workers on any of the shifts. Day workers reported the best appetite, while the poorest appetites were seen among afternoon and rotating shift workers. A greater incidence of alcohol consumption, sick absence, and work related injuries, was seen in shift workers, especially those on rotating and night shifts, than in day workers. Shift work was not related to self reported health complaints or self reported chronic disease conditions. The authors conclude that of all the work shifts, the rotating work shift was the most detrimental to worker safety and health.