The c-Ha-ras-1 locus was analysed in cervical cancers and shown to exhibit the loss of one allele in 36% of heterozygous tumours and a mutation at codon 12 in 24% of tumours at advanced stages. 40% of tumours with mutation contained also a deletion. A c-myc gene activation was found in 100% and 70% of tumours containing mutation and deletion respectively. This suggests that the two proto-oncogenes cooperate for the progression of cervical cancers. Furthermore as more than 90% of these tumours contained also human papillomavirus sequences, our data strongly suggest that multiple genetic events are involved in the genesis and progression of most cervical cancers.