150 years after the first description of the clinical picture of "white blood" and the introduction of the term "leukemia" by R. Virchow it appears, that the leukemias, and the acute leukemias in particular, serve as an impressive example for the major improvements that have been achieved in the treatment but also in the understanding of the biology of malignant dis orders. The international symposia "Acute Leukemia" which are held at Münster since 1986 have developed into an international forum to review the current progress and the future perspectives of leukemia research and therapy at a high scientific and clinicallevel. Since the possibility for active participation in these symposia is somewhat restricted we are glad to have the opportunity to extend the information that was presented at the symposium "Acute Leukemias V - Experimental Approaches and Management of Refractory Disease" which was held from February 27 to March 2, 1994 to a broader audience of basic scientists and clinicians. This meeting was especiaIly designed to discuss experimen­ tal approaches and the management of refractory disease which allows to evaluate new experimental therapies on the basis of preclinical studies.