For studying protein trafficking in Babesia-infected erythrocyte, we describe the cloning of a Rab5, one of molecular marker for vesicle trafficking in eukaryotic cells, gene homologue in Babesia gibsoni (BgRab5). The full-length cDNA of BgRab5 is 1,020 bp long with an open reading frame encoding a protein of 220 amino acids. The deduced amino acid sequence of BgRab5 contained the highly conserved GTP-binding consensus sequence and shares about 40% homology with that of Rab5 from Plasmodium falciparum, Toxoplasma gondii, Dog, Lotus japonicusor, Oryza sativa. Northern blot analysis showed that the BgRab5 probe hybridized with a 1kb band in total RNA from parasitized erythrocytes, that was consistent with the size of the BgRab5 full-length cDNA.