Summary. Self-perceived menstrual patterns have been investigated in a sample of 2115 women aged 18–9 years using a postal questionnaire. Seven aspects of ‘abnormal’ menstruation were denned: prolonged periods, heavy periods, frequent periods, irregular periods, intermenstrual bleeding, painful periods and severe premenstrual syndrome. Women who used oral contraceptives were less likely than other women to report any of the seven menstrual abnormalities except for intermenstrual bleeding and severe premenstrual tension. Women who used an intrauterine contraceptive device (IUCD) reported prolonged, heavy, and frequent periods and intermenstrual bleeding more often than other women, but they did not report painful periods with undue frequency. Women who had had a tubal sterilization generally reported menstrual patterns similar to, or slightly less favourable than, women using no contraception or contraceptive methods other than the pill or the IUCD. There was a significant association between smoking habits and each of the abnormal menstrual patterns except for severe premenstrual tension. In every case, the effect of smoking was unfavourable and in almost every case, current smokers reported the worst experience, with ex-smokers occupying an intermediate position. We believe that these data are of considerable clinical significance and that they offer a basis for a conservative approach to managing menstrual disorders in some women.