To get the necessary information we used of a questionnaire contain 21 question. To get the demographic and sleeping pattern information, two kindsof questions have been considered.12 questions were about demographic characteristics, 13questions were about sleep disorders and pattern of personnel in different shifts.The samples were 764 nurses personnel.

The research results showed that there is a meaningful difference between the rate of sleep disorders of those who have fixed alternative shifts(one month in the morning, one month in the afternoon, one month at night)with those who have inverse alternative shifts (night and morning).

We suggest to hospital directors to review their scheduales and consider the following points as much as possible.

1. - use the fast alternative system (2 morning shifts,2 afternoon shifts, 2 night shifts and 2 days off).

2. - night work hours shoud be reduced from 12 hours to 8 hours to reduce the stress and sideeffects of work.

3. - the shifts should be clockwise(morning-afternoon-night) and not anticlockwise (morning-night-afternoon).