The theory that an imbalance in the control of the cell cycle contributes to the appearance and progression of neoplastic disease is gaining more ground all the time. This new line of research into tumor disease is a result of the progress made in the comprehension of cell death (apoptosis) and the discovery of alterations in the apoptotic pathway in patients with cancer, which have also been correlated to disease mechanisms. Alterations in the cycle of events that brings about apoptosis can result in tumor cells resistant to chemotherapy. In fact one of the inherent risks of chemotherapy is the generation of new, more aggressive, clonal variants and destruction of healthy cells with deleterious effects on the organism. This review examines the results of studies concerning the identification of the alterations in apoptotic mechanisms in carcinogenesis and the mechanisms governing their regulation. The aim was to evaluate if such data could be of use in identifying drugs able to improve cancer treatment.