Ras oncogenes are activated by point mutations occurring in codons 12, 13 or 61 and almost any base pair mutation occurring within the first two positions of any of these codons results in activation of the gene. Although ras point mutations have been reported to occur in several skin neoplasms including squamous carcinoma, keratoacanthoma and melanoma, their frequency of occurrence in basal cell carcinoma is not known. We examined basal cell carcinomas from 13 patients for activating mutations in the H-ras-1 gene by automated direct sequencing of polymerase chain reaction assay amplified targets. We amplified sequences in exon 1 that flanked codons 12 and 13 and amplified sequences in exon 2 that flanked codon 61. The PCR products were centrifuged and directly sequenced using antisense primers in an automated sequencer using fluorescent dideoxyterminators. One tumor was found to show an activating G to A transversion in codon 13 which code for aspartic acid instead of glycine. Although H-ras mutations may be found in some skin tumors, they are not frequent in basal cell carcinomas. From this study we believe that direct sequencing of clinical material is of value and has advantages over other techniques. Additional studies need to be undertaken to understand the true clinical significance of ras mutations in basal cell carcinomas when they occur.