The objective of the treatment of acute leukemia involves the eradication of all neoplastic cells, including the last one. Ideally, treatment should be controlled by monitoring cell kill. If the last cells could be discovered and their biological properties be determined, the qualitative and quantitative effects of treatment should be directly evaluable. This should ultimately permit a calculated tumor cell reduction thereby avoiding overtreatment and excessive toxicity and thus providing a basis for individualized antileukemic treatment. In recent years several new developments have...