In 180 patients with epithelial ovarian cancer and 214 women with benign pelvic pathologies, serum levels of TATI (cut-off point 21 ng ml-1) and CA 125 (cut-off point 35 U ml-1) were determined. Data were correlated with tumour stage, histological type and tumour grade. Overall, when used as a single marker, TATI showed a sensitivity of 63% and a specificity of 72%, whereas the sensitivity and specificity of CA 125 > 35 U ml-1 were 80% and 82% respectively. A combination of the two markers increased the sensitivity to 91% (TATI > 21 ng ml-1 or CA 125 > 35 U ml-1), whereas the specificity decreased to 65%. TATI was clearly superior in diagnosing mucinous carinomata of the ovaries; the rate of true positive findings was 64% versus 50% for CA 125. Unlike CA 125, TATI levels correlated well with tumour grade. In conclusion, CA 125 remains the single tumour marker of choice in the diagnosis of malignant epithelial ovarian cancer, while TATI appears to be a valuable complementory marker with a higher sensitivity in cases of poorly differentiated and mucinous carcinomata.