To determine if ovarian cancer patients would be suitable for MAGE-peptide vaccine-based immunotherapy, the frequency of expression of the MAGE-1-4 genes in ovarian tumours was assessed using reverse transcription polymerase chain reaction (RT-PCR) and product verification with digoxigenin-labelled oligonucleotide probes specific for each MAGE gene. In addition, the frequency of expression of more recently discovered tumour antigens (BAGE, GAGE -1, -2 and GAGE -3, -6) was established using RT-PCR and ethidium bromide staining. In this study 1/16 normal ovarian tissue specimens and 11/25 benign lesions expressed MAGE-1. In non-malignant tissue there was preferential expression of MAGE-1 in premenopausal women. A total of 15/27 malignant specimens expressed MAGE-1, including 10/14 serous cystadenocarcinomas. Expression of other tumour antigens was infrequent. The finding of MAGE-1 expression in both benign and malignant tissue questions previous assumptions regarding the role of MAGE genes in carcinogenesis. In addition, preferential MAGE-1 gene expression in non-malignant premenopausal tissue suggests that the MAGE genes may be involved in cellular proliferation as opposed to carcinogenesis or possibly that MAGE gene expression is under cyclical hormonal control. Finally, this study indicates that serous cystadenocarcinomas may be suitable tumours for MAGE-1 peptide immunotherapy.