Premenstrual syndromes defined by symptom-sets. An analysis is made of the pattern of presenting premenstrual symptoms in randomly selected general practice patients from the Wellington region, New Zealand. Participants, 1826 healthy women 16-54 years old whose characteristics were reasonably representative of the adult female population, were asked about their general, obstetrical and gynaecological health. For the 1456 women who had menstruated within the last month or so, detailed questions were asked about the last menstrual cycle. Each woman was assigned to one of seven premenstrual symptom sets. Three groups had 'pure' symptoms, ie a predominant single symptom (breast tenderness, bloating or irritability). Three groups had 'mixed' symptom-sets. The largest of the 'mixed' groups was formed by the women who reported breast tenderness, bloating and irritability together with tension and depression. Women in this group were most likely to rate their symptomatology as severe. The last group contains a large number of women with miscellaneous symptoms. Characteristics of these groups are outlined. The study highlights the importance of distinguishing among premenstrual syndromes as this can foster more effective clinical management. 