A new plasma protein, tetranectin, was discovered in 1986. It is composed of four non-covalently linked identical peptide chains, each with a molecular weight of 20 kDa. The protein structure is known and it has been found to bind to plasminogen, Ca++ and sulphated polysaccharides. All normal epithelial and mesenchymal cells contain tetranectin in their cytoplasm, but tetranectin is not seen in normal extracellular matrix. The concentration of tetranectin in blood from healthy individuals is about 10 mg/1 with slight sex and age variations. The biological function of the protein is still unknown. The amount of tetranectin in the blood is reduced in patients with various cancer diseases. The degree of tetranectin reduction in the blood from patients with ovarian carcinoma and metastasizing breast carcinoma correlates with survival. While tetranectin is absent in normal extracellular matrix, it is found extracellulary in granulation tissues and in some carcinomas of the breast and the ovary. Lifetables of patients with ovarian carcinoma show that high concentrations of extracellular tetranectin is associated with a poor prognosis. Tetranectin may be a new prognostic marker which should be included in future clinical studies evaluating the prognosis for cancer patients.