We quantified the histologic features of 100 consecutive dysplastic nevi. Although there is heterogeneity in the microscopic attributes of dysplastic nevi, certain features that are seen repeatedly should enable the histologic identification of these melanocytic neoplasms. These features include a central dermal nevocytic component with a peripheral extension of a junctional component, elongated epidermal rete ridges, bridging of nests of melanocytes at the dermo-epidermal junction, nests of melanocytes at the sides of rete ridges as well as at their bases, and concentric eosinophilic fibrosis. Cytologic features of melanocytes were not as valuable as architectural features of individual nevi in classifying these lesions. We also provide an atlas of selected histologic features that depicts some aspects of this heterogeneity.