This study explored the relationship between past night-shift work and present quality of sleep, first by a survey and second with standard laboratory recordings. Nurses (n = 479) working on a day or evening schedule answered a questionnaire about past night-shift work and present quality of sleep. An insomnia index, derived from the questionnaire, was elevated for nurses who had worked more than five nights per month for four to ten years. The index was low for the 13 nurses who had worked more than ten years on night shifts. The sleep of 15 day nurses was recorded in the laboratory. Results showed that a high insomnia index was associated with a high number of awakenings, and that former night-shift workers had a significant reduction in slow-wave sleep, whether or not they had subjective sleep complaints. These results suggest that working at night may have persistent deleterious effects on sleep quality when the experience is long and includes a substantial number of night shifts.