The author looked at the impact of choosing to work at night on individual tolerance to shift work. The relative importance of individual circumstances and personality type in influencing this decision was examined. Five hundred eighty-seven nurses and midwives completed measures of physical and psychological health, difficulties with sleep, social and domestic disruption, flexibility of sleeping habits, morning versus evening preferences, and reasons for engaging in shift work. Results high-lighted the advantages of choosing to work at night, rather than engaging in night work as part of a rotating-shift schedule, on tolerance to shift work. The individual circumstances of the shift workers were particularly important in influencing whether they chose to work at night. These results offer some support for the maintenance of permanent night-shift schedules and have implications for the future design of shift systems.