The detection and elimination of tumors by the immune system and the evasive response of the tumor cells are both truly remarkable phenomena involving many cellular and molecular players. The process of tumor elimination begins when the innate immune system is alerted to the presence of tumor cells, following which a whole host of factors are recruited by a variety of processes to target and destroy the tumor. On the other hand, tumor cells attempt to escape elimination by using several different tactics. These include developing immune system avoiding mutations, remodeling the tumor environment and by suppressing immune system components. Tumor response, therefore, is a battle for supremacy between pro- and anti-tumor activities. BD’s flow cytometers and reagents have, and are still playing a key role in revealing the gory details of this battle.