Polymorphisms in the tumor suppressor gene p53 were identified by Southern blots of denaturing gradient gels (melting polymorphisms). Five polymorphisms were identified in white blood cell DNA, with the frequency of heterozygotes varying from 4 to 27%. The strategy of hybridizing the same blots with different probes suggests that two of the polymorphisms are located in the region of exons 5-6 and one is in the region of exons 7-9. This study illustrates the use of this method for analysis of tumor suppressor genes and suggests future applications, such as for the assay of loss of heterozygosity. That assay is used to detect gene deletions in tumors, an important event in human tumorigenesis.