The rapid expansion in knowledge of the pathogenesis of cancer has created several opportunities for novel strategies in anticancer drug development. Unlike conventional cytotoxic chemotherapy used in routine clinical practice, many of these potential new agents represent non-cytotoxic modulators that target identified molecular abnormalities associated with malignancy. As these therapies evolve from the laboratory towards clinical use, the challenge for oncologists is to determine whether their potential can be matched by substantial improvements in clinical outcome.