We performed FOLFOX 4 therapy in a patient with lung metastasis (a 62-year-old woman) after surgery for rectal cancer and observed both normalization of tumor markers and disappearance of the metastasis. Low anterior resection was performed for progressive rectal cancer, and treatment with UFT and folinate was started one month after surgery. However, tumor markers increased after 2 months of treatment and CT scans showed metastases to both lungs. FOLFOX 4 therapy was started, and tumor markers became normal after four courses, while the lung metastases disappeared after 10 courses. The dosage of FOLFOX 4 was reduced after three courses due to neutropenia and diarrhea. This treatment appeared to be effective for the inhibition of lung metastasis associated with colorectal cancer.