In order to screen interactor(s) of the Aspergillus nidulans α-COP of COPI vesicle, we performed the yeast two hybrid screening by using the gene for A. nidulans α-COP as a bait and identified ε-COP of the COPI vesicle as an interacting protein. The A. nidualns gene for the ε-COP was designated aneA ⁺ (A. nidulans epsilone-COP), which encoded 296 amino acid residues with high level of identity with orthologs from other fungi. Domain analyses with yeast two-hybrid system suggested that the interaction between α-COP and ε-COP relied on the C-terminus of both proteins, and that the N-terminal WD domian of α-COP and the TPR region of ε– COP were not essential but required for the enhancement of the interaction. These results indicate that the interaction mode between α-COP and ε-COP of COPI vesicle is evolutionarily well conserved in eukaryotes.