The expression pattern of the epithelial cell markers MUC1 (CA15-3, EMA), CA125 (OC125), human epithelial antigen HEA (Ber-EP4) and cytokeratins (Ck7, Ck8, Ck7/8, Ck8/18/19) was studied in seven human ovarian cancer cell lines. We analyzed the cell lines by immunofluorescence to determine the surface as well as cytoplasmic expression. Furthermore, we evaluated the mRNA expression of MUC1, Ck18 and Ck19 by reverse transcriptase-polymerase chain reaction (RT-PCR). All cell lines were positive for MUC1. However, expression patterns and staining intensity depended on the different epitope-specific antibodies. CA125, a typical serum marker for ovarian carcinomas, was positive only in two cell lines. HEA was strongly positive in three cell lines, whereas the others expressed the antigen only weakly in the cytoplasm. Ck7 was not expressed in three of the seven cell lines. Ck7/8 was detectable in all cell lines and was strongly expressed in four of them. MUC1 mRNA was expressed by all cell lines as detected by RT-PCR. These findings permit selection of a suitable marker for the detection of disseminated ovarian cancer cells.