A cell line designated HO-8910 was established in vitro from the ascitic fluid of a patient with poorly-differentiated ovarian papillary serous cyst-adenocarcinoma. The cell line grew well through 130 passages and showed malignant epithelial morphology under light and electron microscopes. The chromosome number varied widely from 45 to 300 and its model was 54(42%); The DNA index was 1.45 as measured by FCM method; Both of them showed aneuploidy. The cell line has the ability to secrete steroid sex hormones and also has hormone receptors. When transplanted into nude mice, the xenograft has similar pathological characteristic to the original. It is expected that this cell line would be of great help in the future study on ovarian carcinoma.