In the highly industrialized countries about 20% of all workers have to do shiftwork including nightshifts. Furthermore about half of the shift- workers also have to work at weekends (so-called continuous shiftwork). There are social, economic or technological reasons for shiftwork. Many shiftworkers complain of disturbances of wellbeing, sleep, appetite and performance whereas only a few persons have to expect special illnesses like ulcera of the gastric intestinal system. The main problem of shiftwork is the question of adaptation of the circa- dian rhythms of physiological functions to the phase-shifting of work and sleep. Factors concerning social situation and personality as well as other social interactions are important as intervening variables. The best way to cope with the practical problems of shiftwork is a liberal management allowing the worker to choose the form of work he prefers (day- shift, shiftwork, continuous work). Thus people who are not able to adapt to shiftwork (about 10-20% of the shiftworkers) may leave shiftwork in time to prevent the occurence of illnesses.