To estimate the efficacy of Gemcitabine monotherapy compared to UFT as the post operative adjuvant chemotherapy for completely resected non-small cell lung cancer.

Inclusion Criteria:

1. completely resected non small cell lung cancer
2. no prior anti cancer treatment for thoracic malignancy exept for this operation
3. pathological stage IB, II, and stage IIIA with only one station of n2 disease
4. PS 0-1
5. age 20-75
6. adequate organ function for chemotherapy
7. written informed consent

Exclusion Criteria:

1. small cell lung cancer or low grade malignancy of lung cancer
2. incomplete resection
3. apparent interstitial pneumonitis at chest rentogenogram
4. inadequate condition for chemotherapy