OBJECTIVE:To examine associations between cigarette smoking and menstrual symptoms and miscarriage among young women. METHOD:The study sample consists of 14,779 women aged 18-23 years who participated in the mailed baseline survey for the Australian Longitudinal Study on Women's Health, conducted in 1996. The main outcome measures are self reported menstrual symptoms and miscarriages. RESULTS:Current smokers and ex-smokers had an increased risk of menstrual symptoms and miscarriages compared with women who had never smoked, with the highest risk occurring in heavy smokers (adjusted odds ratios for those smoking > or = 20 cigarettes per day: premenstrual tension 1.5 (95% confidence interval 1.3 to 1.7), irregular periods 1.5 (1.3 to 1.8), heavy periods 1.6 (1.4 to 1.9), severe period pain 1.5 (1.4 to 1.7), one or more miscarriages 2.0 (1.5 to 2.8). The odds ratios generally increased with numbers of cigarettes smoked and a younger age of starting to smoke. CONCLUSION:This study suggests that young women who smoke are at higher risk of a range of menstrual problems and miscarriage than those who have never smoked. The immediacy of this risk (in contrast to the longer term risks of chronic disease) can be used to improve the relevance of anti-smoking campaigns targeted to young women.