About 25-40% of the patients with stage I non-small cell lung cancer are not curable by surgery alone. Over the past years many studies on prognostic parameters in patients with lung cancer have been published in order to identify those patients, who require an adjuvant therapy. The critical assessment of these reports especially of those based on a certain geno- or phenotype of the primary tumor demonstrates that a number of different methods have been used and that the results are sometimes inconsistent. Therefore, a final conclusion seems not to be justified at this time. Recent reports describing sensitive immunocytochemical assays for the detection of early disseminated tumor cells in regional lymph nodes or bone marrow seem to be encouraging. These assays might be useful to identify patients at risk and the repeated analysis of bone marrow samples could be applied in follow-up studies to monitor the efficiency of adjuvant systemic therapies against minimal residual disease. In conclusion, the analysis of a single prognostic parameter seems to be insufficient to identify all patients at risk in stage I lung cancer. Thus, the establishment of a standardized profile of several risk factors based on a prospective, multicenter evaluation appears to be mandatory.