The Authors treated twenty-eigth women using IUD, who suffered from increased menstrual blood loss and pelvic pain, with a prostaglandin synthetase inhibitor, Suprofen, in an attempt to reduce their symptomatology, in a double blind crossover study.The drug produced an important reduction of the menstrual blood loss and pains. These ob-servations suggest that prostaglanclins are involved in the etiology of excessive menstrual blood loss and pains, and that prostaglandin inhibitors may be useful for reducing these symptoms.