Apoptosis is essential in the pathogenesis of hematological diseases. A tumor develops, if the balance between cell division and cell death is disturbed. In recent years many genes involved either in blocking or inducing this process have been identified. Additionally, several cytokines which influence apoptosis have been found. Some of these cytokines could also play a role in the development of resistance to chemotherapeutic agents. Many anticancer drugs exert their action via apoptosis. A strategy to selectively induce apoptosis of tumor cells without altering healthy cells and thus reducing the side effects of therapeutic regimens is a major goal for future development of new therapeutic techniques. Blocking the factors which are responsible for resistance is another promising therapeutic approach and could further improve the clinical outcome and finally prolong the life of patients.