The precise role of the use of adjuvant chemotherapy in the treatment of primary breast cancer has been questioned by some clinicians. One of the most important questions regarding the use of adjuvant chemotherapy is the identification of appropriate patients to receive it. The presence of positive axillary nodes has been the determining factor for the evaluation of chemotherapy in clinical trials. The possibility that other factors should be considered in deciding on the routine use of chemotherapy is discussed here on the basis of data from breast cancer patients diagnosed in the Province of Saskatchewan, Canada, none of whom received chemotherapy as part of their primary treatment. The data illustrate the prognostic heterogeneity that exists among patients with negative axillary nodes and among patients with positive axillary nodes. The implications of such heterogeneity include the possibilities that some patients may not benefit from adjunctive chemotherapy and that some may actually be harmed by it. Specific procedures are described for the analysis of existing clinical trial data to determine whether there is any evidence that some patients may not have benefited from adjunctive chemotherapy. Additional clinical trials would have to be done to substantiate such observations.