AQP10 is the newest member of aquaporins in mammals and expressed selectively in the duodenum and the jejunum in human functioning as aquaglyceroporin. Here we report the cloning of the mouse AQP10 gene. The gene is composed of six exons and spans 5.2 kb. The arrangement of the exons is well conserved between mouse and human. However, the initiator methionine is lost because of the mutation at the translation-initiation site. An insertion of four thymine residues in exon 2 and a deletion of a cytosine residue in exon 5 shift the reading frame. Moreover, aberrant exon/intron junction sequences of introns 2, 3, and 4 also shift the reading frame between exons. Genomic Southern blot revealed the mouse AQP10 gene as a single copy gene. The results indicate that the mouse AQP10 gene is a pseudogene. Furthermore, the mouse AQP10 transcript was not detected in the jejunum where the human AQP10 is strongly expressed.