The last ten years have seen the publication of a vast amount of data regarding cellular resistance to drugs in cancer cells. Recent studies have demonstrated that drug resistance assays appear to be predictive of clinical response and suggest that clinicians should now be considering the potential applications of these assays in the treatment of patients with hematological neoplasms. This collection of papers from the International Symposium on the Clinical Value of Drug Resistance Assays in Leukemia and Lymphoma, Amsterdam, 1992, provides a state-of-the-art discussion on drug resistance assays and their role in the design and individualization of treatment protocols.