A young female presents with crampy, laborlike pains that began shortly before or at the onset of the visible bleeding of her menstrual period. The pain is focused in the lower abdomen, low back, suprapubic area, or thighs and may be associated with nausea, vomiting, increased defecation, headache, muscular cramps, or passage of clots. The pain is most severe on the first day of the menses and may last from several hours to days. Often this is a recurrent problem, dating back to early menarche. Rectal, vaginal, and pelvic examinations disclose no abnormalities.