Inactivation of p53, a tumor suppressor gene, contributes to the genesis and/or progression of a substantial fraction of all human cancers, including > or = 50% of breast, lung, and colon carcinomas. Mutated p53 alleles typically contain missense single-base substitutions within exons 5-8 and encode abnormally stable p53 proteins that accumulate to high levels in tumor cell nuclei. To evaluate the frequency, type, and clinical significance of p53 mutation in human prostate cancer, archival tumor material from 150 prostate cancer patients was examined by immunohistochemistry (IHC) with anti-p53 antibodies. Abnormal nuclear p53 accumulation (IHC) was observed in 19 tumors (12.7%) and was strongly related to disease stage (23% of 69 stage III or IV tumors were IHC+ versus 4% of 74 stage 0-II tumors; P < 0.001, Fisher's exact test). The methods of polymerase chain reaction, single-strand conformational polymorphism, and direct sequencing were used to identify mutations, predominantly missense single-base substitutions in exons 5, 7, or 8 in 9 of 14 IHC+ cases but in none of 20 IHC- cases; 5 of these mutations were G:C-->A:T transitions at CpG dinucleotides. These data indicate that mutated p53 alleles are quite uncommon in early prostate cancers but are found in 20-25% of advanced cancers, suggesting a role for p53 mutation in the progression of at least a subset of prostate cancers.