KIF3A is a member of the kinesin superfamily proteins (KIFs), but its gene has been cloned only in mouse and sea urchin. We have cloned a homolog of KIF3A from the frog, Rana rugosa (rrKIF3A). The sequence encoded a 699 amino acid protein that shares 93% similarity with mouse KIF3A (mKIF3A) and 69% with sea urchin kinesin-related protein (SpKRP85). The putative ATP-binding domain was completely identical to that of mKIF3A and SpKRP85. The level of rrKIF3A mRNA appeared to be high in the brain and testis of adult frogs, but low in the heart, lung and kidney. The results suggest that the rrKIF3A gene is expressed in the brain and testis more than other tissues of adult frogs examined, and that KIF3A is widely distributed in eukaryotic organisms.