The purpose of this study is to identify the presence of the circulating antibodies directed toward ovarian proteins{antiovarian antibodies, AOA) and the nature of antigenic ovarian structure by comparing the binding activities to 4 types of ovarian proteins, particulated and solubilized forms of pig ovarian and granulosa cell membranes in sera of patients with premature ovarian failure(POF) and to evaluate the usefulness of circulating AOA as a follow up tool after treatment. Measurements of AOA were performed by enzyme linked immunosorbent assay(ELISA) in sera of 58 patients with POF, 51 had normal chromosomes and 7 had X chromosome abnormalities. Sera of 21 natural menopausal women and 17 castrated women were also tested and sera of 32 healthy premenopausal women were served as controls. ELISA reactivities against particulated porcine granulosa cell membrane proteins was the greatest among 4 different ovarian proteins. Fifteen(29%) of 51 POF patients with normal chromosome and 1(14.3%) of 7 POF patients with X chromosome abnormalities had AOA while none of 32 controls and 21 natural menopausal women and 17 castrated women had AOA. One POF patient with 47, XXX was identified AOA positive. The ELISA reactivities were followed up monthly up to 5 months in 4 AOA positive POF patients after estrogen-progestin{E-P) therapy. There was a decreasing tendency of the ELISA reactivities in all these patients after E-P therapy and two of them converted to AOA negative. These data suggest that antigenic structure may be components of granulosa cell membrane and the determination of circulating AOA may be useful in the follow up after treatment in patients with autoimmune POF.