A plan is described for the cooperation of 48 departments of surgery under the auspices of the National Cancer Institute in a study of the effectiveness of chemotherapy as an adjuvant to the surgical treatment of cancer. It has three aims: to improve the prognosis of the patient with cancer, to determine whether certain chemical agents are curative, and to develop workable techniques for therapeutic trials. Two investigations specifically planned relate to the use of Thio-TEPA (triethylenethiophosphoramide) in resectable gastric carcinoma and of nitrogen mustard in resectable pulmonary carcinoma. The results of animal research encourage such work, since small tumors have been found more susceptible than larger ones to regression, and the probability of metastasis is less when the number of neoplastic cells in the primary tumor is small. The plan includes the use of standard criteria of diagnosis, treatment, and measurement of effect; the pooling of data from all collaborating institutions; and the participation of statisticians in designing the study and evaluating the results.