The effects of bright artificial light on the subjective mental state of 10 female nurses working shifts at a university hospital were assessed. We investigated two series of five consecutive workshifts rotations comprising one normal, two night and two evening shifts, using two self-administered rating scales. The subjects were exposed to artificial light, brighter than 3, 000lux, for a total of 30min during each workshift of the second series, whereas they worked under normal lighting conditions (approximately 250lux) during the first series. A three-way layout ANOVA, with repeated measures, revealed that bright light tended to improve eagerness and reduce tension, and improved vigor, eagerness, appetite and impairment (the latter only on the second night) significantly or nearly significantly during night, but not evening, shifts. These results suggest that bright artificial light affects the mental state of nurses during night, but not evening, shift work.