In three experiments, 87%, 75%, and 85% of female C57BL/6N mice developed pulmonary metastases by 50 days after amputation of legs having autochthonous 3-methylcholanthrene-induced sarcomas. No difference in the incidence of pulmonary metastases was observed when autochthonous tumors of short (49--94 days) and longer (95--119 days) latency periods were compared. These metastasizing autochthonous tumors may provide a useful model for studies of metastases and for the evaluation of cancer therapy in a minimal residual disease setting.