Gross and microscopic lesions of experimental simian varicella (Delta herpesvirus) infection in African green monkeys (Cercopithecus aethiops) are described. In stratified squamous epithelium, such as the epidermis, tongue, and esophagus, focal areas of epidermal hyperplasia, ballooning degeneration, and blood-filled vesicle formation with ulceration were apparent. Most visceral organs were involved, and the changes included necrosis, hemorrhage, and characteristic intranuclear eosinophilic inclusions in a variety of cells. A generalized vascular involvement was present with intranuclear inclusions in the endothelial and smooth muscle cells in various organs. The nervous system was normal on gross and microscopic examination. Virus titer and serum transferase values were correlated with the clinical signs of infection.