Leaf areas of four maize (Zea mays L.) inbreds and four of their single-cross hybrids were analyzed in terms of numbers of leaves and lengths and widths of individual leaf blades. These lengths and widths were further analyzed in terms of numbers, widths, and lengths of long abaxial epidermal cells which were determined by microscopically examining pyroxylin leaf surface impressions. There was incomplete dominance for increasing leaf number and overdominance for increasing individual leaf blade area. Overdominance for individual leaf area resulted from the complementation of incomplete dominance for increasing cell length and width and overdominance for cell number in the length and width. Thus, both complementation of dominance effects and over-dominance for increased mitotic activity were involved in heterosis for leaf area in maize. The study demonstrates the simplicity of reducing leaf area into its cellular components. This type of leaf area analysis may be useful to breeders attempting to increase the leaf area of maize since it reduces the complex, polygenic trait of leaf area into easily measured components which will display less complex inheritance patterns.Key words: Zea mays L., corn, anatomy, hybrid vigor