We searched for possible mutations in the entire coding region of tumor suppressor gene p53 in primary human renal cell carcinomas using polymerase chain reaction and single-strand conformational polymorphism analysis of RNA. We found p53 mutations in 2 of 21 cases (10%). DNA sequencing of the polymerase chain reaction products verified that the first case included a 17-base deletion at the beginning of exon 6. The second case showed a T to C transition at nucleotide 1328 in exon 7. No clinical or pathological similarity was found in the renal cell carcinomas containing the mutated p53 genes. Present results suggest that p53 mutation is involved at low frequency in human renal cell carcinomas.