The effect of water stress on upper and lower epidermal cells of cotton leaves was evaluated using stereological analysis of light and electron micrographs. These techniques derive three-dimensional information from a consideration of two-dimensional images, in this case from our micrographs. The midday water potentials of the nonstressed and stressed plants were -13.5 and -26.5 bars, respectively. There was no significant difference in the paradermal areas of upper and lower epidermal cells, therefore, it was concluded that the small leaves of stressed plants resulted from an inhibition of epidermal cell division similar to the stress-induced inhibition of palisade cell division previously reported (Berlin et al., 1982 Plant Physiol. 70: 238). The volume of the cell wall was reduced by water stress in both upper and lower epidermal cells. Both epidermal cell types of stressed plants had reduced mitochondrial volumes and reduced surface areas for ER and Golgi membranes. These effects were more pronounced in the upper epidermal cells. Stress produced a reduction of cytoplasmic lipids in the upper epidermal cells and an increase in these bodies in the lower epidermal cells. We conclude that different cell types within the leaf react differently to water stress. These morphological differences have functional correlates, some of which are known and some that can only be speculated at this time.