Objective: The purpose of this study is defining the condition of menstruation period in retarded girls in a psychotherapeutic center in Shahreza. Method: Through a descriptive method, 188 female retarded girls ageing 14 to 60 years, were studied. To collecting the data, a questionnaire including 21 questions on personal characteristic, and 15 questions pertaining to menstruation condition was used. Questioners were completed by nursemaid during 2 months. Results: Analyses showed that majority of women (89/4%) have menstruation period and the majority is not defined whether which one of syndrome symptoms before menstruation they have. 59.6% had regular period and 78.26% did not have any information how to keep clean themselves during period, and the motherly (nursemaid) did this for them. Conclusion: Women with mental retardation need training on menstruation and how to keep themselves clean.