The use of the mucin-specific lectin from Sambucus sieboldiana (SSAM) in the detection of tumor-associated serum antigens produced by patients with ovarian, cervical, and uterine cancer was investigated. Two-site assays were developed which used either SSAM or the MUC1 core protein-specific monoclonal antibody (mab) BC2 as capture, and biotinylated SSAM to detect bound mucin (SSAM and BC2SSAM assays respectively). These new assays were compared to the CA125 assay, and another assay for MUC1 (CASA), which utilizes the core protein reactive mabs BC2 and BC3. some asymptomatic women and patients with benign disease showed very high levels in the SSAM assay, while this was not the case in the other assays. When cutoff levels were set to exclude healthy women and patients with benign disease, the levels of detection in patients with ovarian cancer were 51% with CASA (> 6.7 units/ml), 71% with CA125 (> 250 units/ml), and 38% with BC2SSAM (> 8.6 units/ml). The levels of detection in cervical and uterine cancer patients were 28% and 25% with CASA, 0% and 8% with CA125, and 28% and 25% with BC2SSAM respectively. Of particular interest was the very different spectrum of reactivity observed with the CASA and BC2SSAM assays which use the same capture mab, indicating that each assay detects different glycoforms of the MUC1 mucin. Indeed, when used in combination, the CASA and BC2SSAM assays gave 62% of ovarian cancer patients, and 50% of cervical or uterine cancer patients with elevated marker levels. The additional use of BC2SSAM gave no advantage over the combined use of the CASA and CA125 assays in ovarian cancer, with 80% of patients detected, but the CASA/BC2SSAM combination was particularly useful in the cervical and uterine cancers due to the low level of detection with CA125. In fact, the additional use of CA125 gave no advantage over the CASA/BC2SSAM combination in these patients. Furthermore, the BC2SSAM assay may also be useful in monitoring patients with high preoperative BC2SSAM levels (> 10 units/ml), since this assay predicted recurrence in 5/5 cases, and was negative in all cases with no evidence of disease. Furthermore, the performance of this assay in monitoring these patients was equal or superior to CA125 and CASA.