Two cloned Drosophila sequences, Dash and Dsrc, were previously isolated by hybridization to the viral oncogenes v-abl and v-src. We report that the Drosophila DNA sequences are more than 50% homologous to 700 base pairs of the vertebrate oncogenes that are essential for kinase activity of the v-abl and the v-src gene products. Alignment of the predicted amino acid sequences in the homologous regions shows amino acid sequence identities of 74% between Dash and the 5' portion of v-abl and of 54% between Dsrc and 3' portion of v-src. Comparison of the Drosophila and vertebrate sequences identifies amino acids that may be essential for the distinct functions of the c-src and the c-abl gene products and places the gene duplication event that has generated the two genes prior to the Chordate-Arthropod divergence.