The taxonomic status of Mustela itatsi Temminck, 1844 is discussed. The Jap
anese weasel was considered as a Mustela sibirica subspecies. Twenty-three
measurements of skulls in Japanese and Siberian weasels from different habi
tats were analyzed. The discriminant analysis revealed a significant differ
ence between these two forms. The difference is greater than that between d
ifferent populations of the Siberian weasel from the whole Siberian territo
ry and from the Far East. M. itatsi is distinguished from M. sibirica by it
s smaller and narrower skull. The morphotypic features, size, coloration of
skull, and bacula, were also studied. The taxonomic status of M. itatsi as
an independent species is confirmed by cytogenetic data.