Pretreatment serum levels of the antigens CA-125, tissue polypeptide Antigen (TPA), carcinoembryonic antigen (CEA), and placental alkaline phosphatase (PLAP) were determined in samples from 295 women with adnexal masses. At laparotomy 48% of patients had epithelial ovarian carcinoma, 9% had tumors of low malignant potential, and 8% suffered from malignancies of other kinds. The sensitivity of CA-125 with 35 U/ml as the cutoff was 88% in women with ovarian carcinoma, but 74% among those with limited disease and 58% in borderline malignancy. Only 6 of 17 mucinous ovarian carcinomas were detected. Specificity was 83%. CEA was elevated above 5.0 micrograms/liter in 15 of 17 patients with mucinous ovarian cancer. TPA detected advanced stages of malignancy, but the sensitivity was low, 53%, in cases with limited disease. PLAP was elevated in 46% of ovarian carcinoma patients. For detecting malignancy overall, the use of a parallel combination of the CA-125 and CEA assays was more sensitive than use of CA-125 as a single marker. This test combination may be of value in the diagnosis of adnexal masses. The predictive value of a positive result was 90%, and that of a negative result, 76%.