Human PEX1 (HsPEX1) is the causative gene for peroxisome-deficiency disorders such as Zellweger syndrome of complementation group I, encoding the peroxin, Pex1p, a member of AAA family. Pex1p tagged with an epitope flag was expressed in wild-type Chinese hamster ovary (CHO) cell, CHO-K1. Pex1p was localized in the cytoplasm, as assessed by immunofluorescent microscopy. Cell-lysate of HsPEX1-transfected CHO-K1 was incubated with in vitro synthesized 35S-labelled Pex6p, an AAA family peroxin. Immunoprecipitation of Pex1p using anti-Pex1p antibody resulted in concomitant recovery of 35S-Pex6p. Conversely, 35S-Pex1p was obtained in immunoprecipitate from CHO-K1 expressing human Pex6p, using anti-Pex6p antibody. These results strongly suggest that Pex1p and Pex6p interact with each other.