The decade of the 1990s will see an increasing emphasis on the modulation of chemotherapeutic drug selectivity and in the 'lock and key' approach to new targets to control malignant proliferation. The contents of this volume appropriately reflect these scientific undercurrents. An emerging powerful tool of molecular pharmacology is described by Holcenberg and Wu. Manipulation of genetic expression by modification of messenger RNA is now within our reach, and the basic concepts are suc- cinctly reviewed as a primer on future biochemical engineering of new anti- cancer molecules. Another concept that appears to be worthy of further study in both experimental and clinical chemotherapy concerns obs'ervations on the modulation of activity by the nucleoside transport inhibitor, dipyri- damole. How potentiation of several anticancer drugs occurs has practical, as well as theoretical, ramifications, discussed by Goel and HowelL Finally, O'Dwyer and La Creta present a fresh look at sensitization of chemotherapy by the hypoxic radiosensitizer, SR-2731.