Our study aimed at screening patients with primary Sjogren's syndrome (pSs) for the presence of antiovarian antibodies (AOAs). Detection of AOAs in patients' sera was achieved by ELISA, using bovine ovarian extract for coating. Western blot analysis and immunohistochemistry were used to characterize the antibody targets in the extract and to determine their locus on the bovine ovary, respectively. Specific AOAs were detected in 27% of 37 patients (two with premature menopause) and in none of the controls. Immunoreactivity mainly resided in five proteins of the extract with molecular masses 42, 49, 55, 64 and 72 kDa, and it might be attributed to their carbohydrate components. The antibody targets were mainly located in the granulosa and theca interna cells of the follicle, and in the endothelial cells and fibroblasts of corpus luteum. The detection, for the first time, of AOAs in a significant percentage of patients with pSs may suggest autoimmune oophoritis, clinical or subclinical.