Serum or plasma total sialic acid (TSA) and lipid bound sialic acid (LSA) are useful markers for human cancer. In this study, sialic acid levels have been demonstrated in various types of human cancer including brain, thyroid and Hodgkin's. TSA was found to be significantly elevated in various human brain tumors, especially in the microsomal fraction. Also serum and tissue LSA levels indicated significant increases when compared to the normals in various brain and thyroid tumors. TSA levels were significantly higher in the plasma and leucocyte in patients with Hodgkin's. The results show that sialic acid can be advisable as a beneficial marker for detecting malignancies. But it can not be used as a criteria for identifying tumor types.