Mammalian skin is regularly exposed to different environmental stresses, each of which results in specific compensatory changes in protein expression that can be assessed by proteomic analysis. We have established a reference proteome map of BALB/c murine skin allowing the resolution of greater than 500 protein spots in a single two-dimensional polyacrylamide gel. Forty-four protein spots, corresponding to 28 different cutaneous proteins, were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and the Mascot online database searching algorithm. Twenty-five proteins were expressed at higher levels in the epidermis, whereas only nine were found predominantly in the subepidermal tissues. A subset of protein spots exhibited strain-specific expression. Proteins of diverse function were identified, including those involved in stress response, apoptosis, growth inhibition, the maintenance of structural integrity, translational control, energy metabolism, calcium binding, cholesterol transport, and the scavenging of free radicals. Prohibitin expression was detected cutaneously, with more abundant protein and mRNA levels in the epidermis. Five molecular chaperones including protein disulfide isomerase, 78 kDa glucose-regulated protein precursor, heat shock protein 60 (HSP60), HSP70, and HSP27 were also identified. Of these, HSP27 expression was confined mainly to the epidermis, and expression of protein disulfide isomerase was found primarily in the subepidermal tissues. Proteomic analysis of skin following heat or cold shock resulted in increased levels of HSP27, HSP60, and HSP70 suggesting involvement of these chaperones in the cutaneous response mechanism to temperature stress. These data establish numerous reference markers within the proteome map of murine skin and provide an important framework for future efforts aimed at characterization of the epidermal and subepidermal responses to environmental changes.