Serum levels of the immunosuppressive acidic protein (IAP) and CA-125 were measured in 45 patients with ovarian tumors (30 malignant and 15 benign) before surgery. Concentrations of both markers were slightly increased in benign forms but still within the upper limit for controls. The sensitivity of IAP in detecting ovarian cancer was higher than CA-125 (83.4% versus 76.7%). Five false negatives were observed in IAP assay and seven for CA-125. Parallel determination of both markers, however, improved the diagnostic accuracy up to 90.0% of the total malignant cases. Combined measurements of circulating IAP and CA-125 are therefore recommended in the detection of ovarian cancers.