The cellular homolog of the oncogene v-src, the proto-oncogene c-src, was cloned from rat testis using a high stringency polymerase chain reaction. Rat c-src cDNA shared identity with chicken and mouse, and Rous sarcoma virus c-src and v-src, respectively. Rat c-Src protein was 98% homologous to both human and mouse c-Src. Interestingly, rat Src contained one extra amino acid compared to the mouse protein. As expected, the rat testis Src lacked the six extra residues common to the neuronal Src identified in human and mouse. Reporting of the cDNA sequence for non-neuronal, rat c-src should facilitate experimentation into cell growth and transformation using rat tissues as models of human disease.