P53 is a tumor suppressor gene that has been implicated in the molecular genetics of many human malignancies. Nucleotide alterations, most commonly single point mutations, have been shown not only to abrogate the p53 suppressor function but also to contribute to the transformed phenotype. We report the detection of a p53 gene mutation in clinical specimens of a patient with relapsing prostate adenocarcinoma 14 years after definitive external beam radiation. The techniques of single strand conformation polymorphism analysis and direct sequencing of polymerase chain reaction generated products were used for this study. Analysis of tissue from different locations of the primary tumor revealed intratumoral molecular heterogeneity; the mutation was absent in 1 area but present in another. Tumor from a regional lymph node metastasis harbored the identical p53 mutation. Furthermore, an additional genetic alteration, an allelic loss on chromosome 17p but not including the p53 gene, was observed only in the metastatic tissue. These observations in clinical specimens of primary and metastatic sites provide evidence for the association of the p53 gene in the progression of human prostate carcinoma.