This book deals with the impotance of sialic acids in Breast Carcinoma and its derivatives and the ratio of total sialic acid to total protein in breast and other cancer patients and comparison of their levels with those of normal individuals and other diseases. Isolation and study the binding characteristics of human cancerous breast lectin to glycoprotein present on the human erythrocyte surface and then determination of the optimum conditions for this binding through the study of the effect of various factors.Purification and identification of lectin from human cancerous breast homogenate, and determination of the molecular weight of purified the physiochemical properties and the effect of various factors on binding activity for purified lectin studied carefully . Furthermore the determination of the kinetic and thermodynamic parameters associated with the binding of lectin to glycoprotein at different temperatures. Estimation of the levels of mucoid and protein-bound hexose in sera of breast and other cancer patients and was studied to compare these levels with those from normal individuals and Asthma diseases as a pathological control.