In order to study the altered molecular events during laryngeal carcinogenesis and elucidate the role of Haras oncogene amplification and mutation. we have examined their profile by polymerase chain reaction （PCR） and selective oligonucleotide hybridization. We analyzed the mutational status of codon 12 of Haras in 22 laryngeal carcinomas and 10 normal tissues. and found that 7 of 22 laryngeal carcinomas contained a Ha-ras mutation at codon 12. The frequency of mutation was 32%. None of the normal tissues revealed mutation. Moreover. no amplification was found in cancers when compared to the normal. Ourfindings indicated that the activated Ha-ras gene existed in laryngeal carcinoma. and activation of the Haras gene by mutation at codon 12 might play a key role in laryngeal carcinogenesis.