The levels of expression of the ras family genes, in 14 tumour specimens from squamous cell carcinomas of the larynx were analysed by reverse transcription-polymerase chain reaction. The H-ras was overexpressed in 12 (86%) samples, K-ras in 11 (78%) and N-ras in 8 (57%) samples. All tumours exhibited overexpression of at least one member of the I-as family. In addition, each member of the ras family was activated independently from the rest of the ras family genes. The incidence of amplification in the ms family genes was also analysed by differential PCR: K-rns was found amplified in 14% (2/14), N-ras in 7% (1/14) and H-ras in none of the samples tested. Amplification data exhibited no association with the expressional levels of the ras genes. Furthermore, we investigated the incidence of codon 12 point mutations in the ras family genes but no mutation was found. The present study indicates that overexpression of the ras family genes is important for the development of the disease and it is not associated with the amplification status of the genes. In addition, the differential regulation among the members of the ms family might play a role in the development of laryngeal tumours.