The delineation of the molecular basis of cancer in general, allows for the possibility of specific intervention at the molecular level for therapeutic purposes. To this end, three main approaches have been developed: mutation compensation, molecular chemotherapy, and genetic immunopotentiation. The strategy of mutation compensation aims to correct the specific genetic defects in cancer cells. Such correction is accomplished by either ablation of oncogenic products, replacement of cellular tumor suppressor genes, or interference with dysregulated signal transduction pathways. A second strategy is molecular chemotherapy, which aims to increase the specificity of drug delivery or to increase tolerance to standard chemotherapeutic regimens. A third strategy, genetic immunotherapy, aims to augment the specificity and/or the magnitude of the normal immune response to tumors. For each of these conceptual approaches, human clinical protocols have entered Phase I clinical trials to assess dose escalation, safety, and toxicity issues.