We examined Southern blot analysis of genomic DNAs from 70 patients with sporadic renal cell carcinoma, using the human L-myc oncogene fragment as a hybridization probe. Our purpose was to study the relationship between the restriction fragment length polymorphism (RFLP) of the L-myc and the frequencies of metastasis. The patients were classified into 3 genotypes according to the polymorphic patterns defined by two alleles (L-L:17, L-S:31, S-S:22). The relative ratios of the 3 genotypes in the renal cancer patients were similar to those seen in healthy Japanese. However, of 20 patients who exhibited distant metastases at diagnosis, only 2 belonged to the L-L type. The incidence of distant metastasis in L-L type patients was significantly lower than that in L-S and S-S patients (p = 0.068, by Fisher's exact probability test). These results basically correspond to the previous findings in the lung cancer patients [Kawashima et al.: Proc. natn. Acad. Sci. USA 85: 2353-2356, 1988]. On the other hand, L-myc RFLP analysis in 50 prostatic cancer patients revealed that the incidence of metastasis at diagnosis did not correlate with L-myc genotypes. L-myc RFLP seems to be less promising in prostatic cancer than in lung or kidney cancer.