Cancer initiation and progression is strongly influenced by the tumor microenvironment consisting of various types of host cells (inflammatory cells, vascular cells and fibroblasts), extracellular matrix and non-matrix molecules. Host cells play a defining role in two major processes crucial for tumor growth: angiogenesis and escape from immune surveillance. The interdependence of these processes resemble the principles of Yin and Yang, as the stimulation of tumor angiogenesis inhibits effective immune responses, while angiogenesis inhibition may have the opposite effect. These considerations may be useful in developing anticancer strategies based on the potentially synergistic combinations of antiangiogenic and immunostimulatory drugs.