Targeted therapies for cancer are discussed. Research into the molecular biology of cancer has revealed critical differences between normal and tumor cells and has pinpointed key processes that regulate the growth and progression of cancers. This has in turn allowed for the development of agents that specifically target these molecules and pathways, particularly those regulating the signaling transduction pathway that controls cell replication, differentiation, tumor metastasis, and apoptosis. Such novel targeted therapies include those that can inhibit the function of cellular growth factors or their receptors essential for signal transduction, block angiogenesis required for tumor growth and metastasis, and antisense strategies designed to suppress the expression of specific genes. These approaches have resulted in clinical benefit for selected tumor types, yet challenges remain such as determining the optimal dose and administration of these agents, alone or in combination with standard cytotoxic chemotherapy, and at what stage of disease they might have the greatest influence.