This review demonstrates that stress is closely related to impaired sleep in cross-sectional studies. In particular, the anticipation of high demands or effort the next day seems important. Sleep recordings show that stress is associated with shortened sleep, fragmentation, and possibly a reduction in sleep stages 3 and 4. Shortened or disturbed sleep causes increases in levels of traditional stress markers (eg, cortisol) and may thus exacerbate the effects of stress. Much knowledge is still lacking, however, particularly about the effects of real-life work stress. The latter requires longitudinal studies in real-life situations.