The evidence that the principles of surgical adjuvant chemotherapy developed in experimental animal systems also apply to a variety of neoplastic diseases in man has been clearly demonstrated. Micrometastatic disease can be eradicated with effective chemotherapy in several diseases. Prolongation of disease-free interval, if not cure, is now possible in diseases in which curative surgery alone or in combination with radiotherapy does not achieve these goals. The previously fatal childhood solid tumors--Wilms', Ewings' sarcoma, embryonal rhabdomyosarcoma--are curable in a high percentage of patients appropriately treated with combinations of surgery, radiotherapy, and chemotherapy. The prolongation of the disease-free interval in osteogenic sarcoma has permitted consideration of entirely new surgical approaches for this tumor in which radical amputation has traditionally been employed. The spectacular results achieved in the treatment of Stage II breast cancer may potentially save hundreds of thousands of lives in the coming decade. Clinically recognizable metastatic disease is rarely curable by any currently available treatment modality. The prolongation of disease-free intervals and production of cures when surgical adjuvant chemotherapy is employed may be partly explained by relatively more circulation, and thus drug delivery to each tumor cell, more favorable cellular kinetics, and a healthier and more immunocompetent host who is better able to withstand drug effects on normal tissues, and to participate in tumor destruction. Cures of certain patients with neoplastic diseases using surgical adjuvant chemotherapy has increased the incentive to learn more about new and old drugs and their effective use alone and in combination. Chemotherapy, in appropriate combinations with surgery, radiotherapy, and immunotherapy, may well be more efficacious in many clinical situations than the traditional use of single-modality treatment. The data presented in this paper relate solid evidence that the possibility of cure in a variety of neoplastic diseases is real.