The productivity of 53 female shift workers, and the sleeping habits of a subsample of 30 of them, were analyzed in order to determine the relative contributions of circadian adjustment and sleep deprivation on productivity. The study was conducted at an electronics component factory in which 186 female shift workers were employed in manufacturing capacitors. Workers were on a weekly rotating shift system, and shifts rotated in the order mornings, nights then afternoons. An individual piece rate incentive plan was in place at the time of the study, with each worker paid a fixed amount for each capacitor of a given type that they produced. This amount was 20 percent higher on the night shift than on the other shifts. Workers were not penalized for rejected capacitors since their incidence was extremely low. Single and married workers slept for the shortest times between successive morning and night shifts respectively, while both slept the longest between successive afternoon shifts. Morning and afternoon shift productivity was relatively constant. Night shift productivity on the other hand was extremely variable, rising dramatically during the first three shifts and then falling off again. The authors conclude that the initial rise in night shift productivity is due to circadian adjustment, and that the subsequent fall is due to sleep deprivation. Since single but not married workers showed decreased productivity when on the morning shift, apparently attributable to sleep deprivation, the authors conclude that social factors may also play a role in productivity.