Lung cancer-predominantly non-small cell lung cancer (NSCLC)-is the leading cause of death from cancer in most industrialized countries. Patients with early-stage NSCLC are at substantial risk for recurrence and death even after potentially curative surgery. Multiple large randomized trials have demonstrated that adjuvant chemotherapy using modern cisplatin-based regimens can significantly improve 5-year survival in carefully selected patients with NSCLC.The current staging system is inadequate for predicting the outcome of treatment and the prognosis in an individual patient. Molecular markers may provide additional information about the likelihood of relapse beyond that obtained from pathologic staging. They may also have value in determining which patients will benefit from adjuvant platinum-based chemotherapy.This is a review focused on approaches and specific markers under study, including gene expression profiles, DNA repair pathways, class III beta-tubulin expression, abnormalities in the k-ras oncogene and p53 tumor suppressor gene, and DNA methylation markers. Additional studies will be required to determine whether these markers are useful in selecting patients for adjuvant platinum-based chemotherapy.