Alpha-1-acid glycoprotein (AGP) is a glycoprotein found in the alpha-1 globulin fraction of human plasma proteins. AGP is an important representative of acute-phase proteins. Although numerous articles have been devoted to AGP, its exact biological function remains obscure. AGP levels increase with a number of diseases. One of them is a tumor disease. In our paper, we discuss the role of increased AGP levels in cancer patients. We deal with the role of AGP as a drug-binding protein and its effect on the efficacy of chemotherapy in oncological patients. Other problems that are discussed in our paper include the role of AGP as an immunomodulatory protein and its relationship to angiogenesis because angiogenesis plays an important role in the progression of cancer (Ref. 57). Keywords: alpha-1-acid glycoprotein, orosomucoid, cancer, disease marker, immunomodulatory protein,drug-binding protein.