The proto-oncogeneyes encodes a protein tyrosine kinase described as a member of the non-receptor protein tyrosine kinases family (NRPTK). We have identified two clones from the genomic library ofDrosophila melanogaster which hybridized to thev-yes oncogene (encoded by the Y73/Esh Avian Sarcoma Virus). These clones represent two different genomic sequences fromDrosophila. By RNA slot blot hybridization, we have demonstrated the presence ofyes homologous sequences in the RNA of larvae (the third instar), pupae and an embryonic cell line ofDrosophila. On northern analysis of the cell line RNA, three transcripts (3.8, 2.0 and 1.0 kb) hybridized with theyes sequence. Oncogeneyes is thus well conserved across widely separated phylogenetic lines like human, chicken andDrosophila indicating involvement in essential biological functions.