The role of adjuvant postoperative therapy for patients who have resected non-small cell lung cancer (NSCLC) has been controversial. Recent large trials and meta-analysis support a modest, but significant, survival benefit for postoperative adjuvant chemotherapy. Postoperative radiation therapy has little potential benefit in patients who have N(0) or N(1) disease and should not be used routinely in these patients. There are suggestions of benefit for patients who have N(2) disease, but adequately powered trials have not been conducted to demonstrate a possible small, but clinically worthwhile, survival benefit in this subgroup. Central nervous system relapse has emerged as an increasing problem for patients who have NSCLC; trials of prophylactic cranial irradiation are underway in several cooperative trial groups.