Serum glycoprotein galactosyltransferase levels were determined in 28 healthy women and 113 patients with ovarian carcinoma with various histological types, at different clinical stages. Ovomucoid, which possesses terminal N-acetylglucosaminyl residues, was used as glycoprotein acceptor. Clinical correlations between galactosyltransferase levels and tumor burden were examined, as well as the variations due to histology. Follow-up studies could be done for 60 patients, and correlations with clinical evolution, established. Galactosyltransferase might be a promising marker for the diagnosis and follow-up of ovarian carcinomas.