Genes, which are implicated in the pathogenesis of human tumors, may demonstrate Restriction Fragment Length Polymorphism (RFLP). Population studies of such RFLP are of potential interest for a genetic analysis of cancer susceptibility. The initial data of Krontiris et al has shown a significant increase of rare c-Ha-ras-1 alleles in individuals with tumors. Since then, other significant associations have been found between other genes RFLPs and various tumors. In this paper, we report that L-myc RFLP may prove useful in identifying breast cancer patients at high risk of developing lung metastases.