The prevalence of dysmenorrhea was studied in a random sample of 19-year-old women from an urban Swedish population. Dysmenorrhea was reported by 72% of the women. Fifteen percent suffered from dysmenorrhea which limited daily activity and was unimproved by analgesics. Dysmenorrhea occurred significantly (p less than 0.01) more often in women not using oral contraceptives. A significant correlation (p less than 0.01) was found between early menarche and an increased severity of dysmenorrhea. There was a significant correlation (p less than 0.01) between the severity of dysmenorrhea and the amount of menstrual flow. Parous women had significantly (p less than 0.01) less dysmenorrhea than women who had never been pregnant or women who had experienced a legal or spontaneous abortion. Smokers as compared to nonsmokers had significantly (p less than 0.01) less dysmenorrhea. The severity of dysmenorrhea was not affected by height, weight, or regularity of the menstrual cycle. Absenteeism as a result of dysmenorrhea was evaluated.