PIP: A case is reported of a 22-year old woman, para-1, gravida-5, with repeated abortions and a finding of endometrial ossification. Bony tissue in the endometrium may be caused by retained fetal tissue undergoing dystrophic calcification and ossification. Squamous metaplasia may originate in mature endometrial cells after prolonged irritation by a foreign body; in this case the postabortal endometritis could have been the irritant. The association of metaplasia and ossification may suggest an etiopathogenic sequence. The effects of the heterotopic bone can be compared to those of an IUD such as irregular bleeding and the repeated early abortions; they ceased only after removal of the bony material from the uterus. The patient subsequently had a normal pregnancy and delivery.