Serum samples from 72 patients with established carcinoma of the breast were investigated for ectopic presence of hPL. Further, the relationship of ectopically-secreted hPL and hCG-beta in breast cancer was investigated. Ten of 72 patients examined had detectable hPL and 12 had detectable hCG-beta, at 1-2 ng/ml serum sensitivity of the assay. The presence of hPL in serum of breast cancer patients was found to be independent of that of hCG-Beta. Sera of 13 patients with cystic mastitis, five with fibroadenoma, two with acute inflammation of breast, 20 normal women (non-pregnant) and 20 normal men did not show any detectable serum hPL or hCG-beta at the above mentioned sensitivity of the assay. Since these hormones were not detectable in normal men, normal non-pregnant women, and in patients having other pathological conditions of breast, the possible use of them as markers in cancer is expected