Background: Perimenstrual syndrome (PMS) among women with an intellectual disability (ID) has not been investigated in Taiwan. This study explores the prevalence/severity of PMS experienced by women with ID who are institutionalised. Method: Ninety two female residents aged 15 to 54 at six public institutions completed a structured interview between June and November 2006, together with the Moos Menstrual Distress Questionnaire (MMDQ). Results: Strong significant differences were detected between the participants' physical, emotional, behavioural, and psychological changes during the perimenstrual and remainder phases in all domains other than "Arousal". Cramps, hot flushes, affection, orderliness, excitement, and bursts of energy/activity were most prevalent during the perimenstruum (greater than 50%). The participants' unique characteristics and cultural context were associated with the various domains of the PMS. Conclusions: Special attention should be paid in future to ascertain whether these experiences and perceptions of PMS are common among all women with ID. (Contains 2 notes and 4 tables.)