Distant metastasis is the predominant cause of death in early-stage non-small cell lung cancer (NSCLC). Currently, it is impossible to predict the occurrence of metastasis at early stages and thereby separate patients who could be cured by surgical resection alone from patients who would benefit from additional chemotherapy. In this study, we applied a comparative microarray approach to identify gene expression differences between early-stage NSCLC patients whose cancer ultimately did or did not metastasize during the course of their disease. Transcriptional profiling of 82 microarrays from two patient groups revealed differential expression of several gene families including known predictors of metastasis (e.g., matrix metalloproteinases). In addition, we found S100P, S100A2, trypsinogen C (TRY6), and trypsinogen IVb (PRSS3) to be overexpressed in tumors that metastasized during the course of the disease. In a third group of 42 patients, we confirmed the induction of S100 proteins and trypsinogens in metastasizing tumors and its significant correlation with survival by real-time quantitative reverse transcription-PCR. Overexpression of S100A2, S100P, or PRSS3 in NSCLC cell cultures led to increased transendothelial migration, corroborating the role of S100A2, S100P, and PRSS3 in the metastatic process. Taken together, we provide evidence that expression of S100 proteins and trypsinogens is associated with metastasis and predicts survival in early stages of NSCLC. For the first time, this implicates a role of S100 proteins and trypsinogens in the metastatic process of early-stage NSCLC.