The association of unilateral tubo-ovarian abscess and the presence or use of an intrauterine contraceptive device(IUD) appears to be a definite clinical entity. Four cases of unilateral tubo-ovarian abscess in patients using the IUD are presented. Three patients had a Dalkon Shield IUD and one had a Lippes Loop. Two patients had unilateral salpingo-oophorectomy while the other 2 had total abdominal hysterectomy and bilateral salpingo-oophorectomy. The differential diagnosis, possible etiology, route and mode of infection, and management are discussed.