Two permanent human ovarian clear cell adenocarcinoma lines (OVISE and OVTOKO) were established from metastatic tumors of two patients who were treated with five to six courses of CAP chemotherapy. The two cell lines grow on monolayers and showed a variety in both size and shape: small or moderately sized cuboidal cells, columnar cells, spindle-shaped cells, and malignant tumor giant cells. The cell lines have been in culture for 4 to 6 years, the passage number varying from 160 to 220. The mean population-doubling time of the two cells was 60 to 70 hr. The OVISE cells shed tumor-associated antigens CA19-9, CA125, and TPA in the culture medium, whereas the OVTOKO cells did not secrete them at detectable levels. Immunohistochemical analysis showed that coexpression of cytokeratins and vimentin was preserved in the two cell lines, which is a feature of cultured epithelial origin. Cytokeratin polypeptides 7, 8, 18, and 19 were expressed in both cell lines. The EGF receptor was more intensely expressed in the OVTOKO cells than in the OVISE cells. The estrogen and progesterone receptors were negative in both cell lines. The two cell lines showed no chemosensitivity to anticancer drugs including cisplatin, doxorubicin, cyclophosphamide, and etoposide. Heterotransplantation of the two cell lines reflected the origin of cells. Intraperitoneal transplantation of the OVTOKO cells yielded peritoneal implantation and distant metastasis, whereas that of the OVISE cells showed no dissemination and metastasis. These new ovarian clear cell adenocarcinoma lines will provide a relevant experimental system for further investigations into the intrinsic alterations responsible for malignant progression and chemoresistance.