The serum levels of immunosuppressive acid protein (IAP) and CA 125 were determined in 98 patients with ovarian cancer, in 20 patients with benign ovarian tumors and in a group of normal postmenopausal women as controls. On the basis of the mean values of normal controls (346.46 ± 133.26 μg/ml), the IAP threshold was fixed at 613 ∣ig/ml. Increased IAP levels were found in 70.4% of patients with ovarian cancer, in 25% of benign tumors and in 4.5% of normal women. Elevated levels of CA 125 were observed in 66.6% of cancers, in 40% of benign tumors and in 6.9% of controls. In particular, in early stage ovarian cancer the combined assay of the two markers increased by about 30% with respect to CA 125 alone. The simultaneous determination of IAP and CA 125 allowed an overall sensitivity of 84% without any significant reduction of specific