Several researchers have already established that chromosomal changes occur in a non-random pattern in non-small cell lung cancer. It appears that these changes correlate with specific genetic changes, resulting in the malignant phenotype. Furthermore, a great deal of experimental evidence supports the multistage theory of carcinogenesis, whereby incremental changes in the genome accumulate, resulting in the malignant phenotype. The final product of the accumulated changes is determined by the cell of origin and the number and severity of changes occurring. We hope to establish that early changes (as expressed by karyotypic changes or by particular point mutations) can be identified which would indicate the likelihood of particular patient developing another malignancy. This information could then be applied to clinical situations, for example, to determine the frequency of clinical follow-up by chest x-ray, screening bronchoscopy, or sputum cytology. Furthermore, the information gathered could help identify one or a few genetic changes necessary for transformation, which could then be explored to further define the transformation process.