Here we report the nucleotide sequence of the canine interleukin-2 (IL-2)-encoding cDNA. Cloning of the canine IL-2 cDNA was achieved by the polymerase chain reaction employing, as a template, a cDNA derived from mitogen-stimulated canine splenic lymphocyte mRNA. The deduced amino acid (aa) sequence of canine IL-2 consists of 155 aa and displays 84% sequence similarity to human IL-2.