Single-strand conformation polymorphism analysis of polymerase chain reaction products (PCR-SSCP analysis) was used for detection of mutations of the p53 gene in surgical specimens of human brain tumors. Six of 45 brain tumors showed mobility shifts in the analyses. These six tumors also showed loss of a normal allele. The samples were examined further by direct sequencing. Results showed that four of them had single-base substitutions and the other two had deletions of one and eight base pairs. Five of the six mutations detected were clustered in highly conserved regions of the p53 gene. The frequency of p53 gene mutations in primary brain tumors examined was 9.8%. We also found two new polymorphic markers in the p53 gene, one in intron 7 and the other in an Alu repeat in exon 11. Both markers could be detected by SSCP analysis. Using these two markers, we found two cases of loss of heterozygosity in other brain tumor specimens. Results suggested that aberrations of the p53 gene were not correlated with the malignancy of some types of brain tumors such as anaplastic astrocytoma and glioblastoma, contrary to previous observations on colorectal cancers.