We characterized evolutionarily conserved J domain containing protein (JDP) genes from human, Bombyx mori, and Manduca sexta. Each of the JDP proteins contains a J domain at its N-terminus and a highly conserved C-terminal domain. Southern blot analysis revealed that the human JDP1 gene is present as a single copy in the human genome. Expression was higher in brain, heart, and testis than in kidney or stomach. Human JDP1 was mapped in silico to chromosome 10q21.1, which exhibits a conserved synteny with the central region of mouse chromosome 10. Drosophila jdp is located at 99F4-99F11 on the right arm of the third chromosome.