Living organisms can respond to a stimulus at 3 levels: (1) the cell; (2) the tissue; (3) the organism as a whole. Although the earliest response to a stimulus is at the cellular level, inflammation is basically a tissue response. By the time an inflammatory disease of the skin is apparent, however, it is too late to observe how the tissue responses evolve to produce the clinical lesion. The purpose of this paper is to present evidence that cytoplasmic glycogen in the human epidermal basal cell may indicate at the cellular level that an inflammatory stimulus has reached the skin before the tissue as a whole has reacted sufficiently to appear inflamed. Three types of experimental stimuli were used: removal of the stratum corneum,1-4,8,10 minimal erythema from the sunburn wavelength of ultraviolet light,5,9 and a horizontal cut through the dermis below an intact epidermis.6,11 As previously described,