This scientific journal article discusses the taxonomic value of mammalian hair. The ability to identify mammals from hair alone is of significance in the fields of criminology and paleontology. Two morphological entities; pelage and skull identify mammals. Pelage (hairs) serve to identify the species by differing in form, size, and pigmentation or by amounts and arrangement. Differences can be detected in the medulla, cortex and cuticular scales. Pigmentation varies in distribution, color and type. This study confines itself to California mammals, 392 species and sub-species. Hairs are taken from two areas; mid dorsum and mid venter from museum specimens by pulling or cutting. Carbon tetrachloride removes extraneous oils and the hairs are then mounted with Canada Balsam. A millimeter scale checks lengths and an ocular micrometer measures width. Dorsum guard hairs possess the most differentiating characteristics. These form the basis of the classification keys. Keys are appended. This is a reference document for the identification of mammalian hair. -- CCI