The aim was to analyze the impact of adjuvant systemic treatment (AST) on the anatomical distribution, the number, and the temporal relationship of the first metastases in 635 patients (pts) with breast cancer. These patients participated in the prospective studies of AST of the Danish Breast Cancer Cooperative Group (DBCG) 77-program. All patients had primary high-risk breast cancer (i.e. node positive or local invasion or tumor size greater than 5 cm). The initial treatment was mastectomy with axillary sampling, followed by postoperative radiotherapy. The types of AST and the number of patients with recurrence were: chemotherapy (CT), 134 pts; levamisole (LEV), 96 pts; tamoxifen (TAM), 154 pts. The pattern of recurrence in these patients was compared with the pattern of recurrence in 251 pts who did not receive AST (controls). Although CT reduced the total number of metastatic sites (P = 0.04), the incidence of liver metastases was increased compared to untreated controls (P = 0.02). The median number of metastatic sites was equal in TAM- and LEV-treated pts compared to controls. The incidence of lung metastases was increased in TAM-treated pts (P = 0.03), and LEV-treated pts had a decreased incidence of lymph node (P = 0.01) and pleural recurrences (P = 0.01) compared to controls. The results may suggest that mechanisms of clonal selection during the metastatic process involve differences in sensitivity to antineoplastic treatments of metastases at various anatomical locations.