This study examined the symtom patterns of women seeking help for Premenstrual Syndrome (PMS) complaints. Seven women who were less than 35 yrs, within 10% of ideal body weight and who had experienced a full-term pregnancy, completed a daily health diary during an ovulatory menstrual cycle. In the luteal phase, symptom summary scores of the PMS group increased (P less than 0.05) and were markedly higher (P less than 0.5) from baseline acyclic scores of four ovulatory women who denied menstrual-related distress. To examine severity changes in individual symptoms, a total of 399 cases representing 57 symptoms from the seven 45-day diaries were evaluated for menstrual cycle entrainment. Of the 246 symptoms that met the criteria for a cycle phase change (62%), the classic PMS pattern of low/high severity was the most common (40%). Seven different subtypes of the PMS pattern were identified; four of these subtypes demonstrated a severity score elevation at ovulation as well as during the premenstruum. For individual women, the majority of symptoms (65%) displayed only two pattern types, suggesting a common rhythmic entrainment of symptom intensity.