The objectives of this study are immunohistochemical detection of the viral antigen and structure of fowl pox virus and developmental stage of inclusion bodies by electron microscopy in experimentally infected chorioallantoic membrane (CAM). Lyophilized fowl pox virus, strain 92 which was obtained from the Veterinary Central Laboratory in Weybirdge, (UK) used in 103 titer. Thirty, 10 days old Specific Pathogen Free (SPF) chicken embryonated eggs chorioallantoic membrane that experimentally infected with this strain. Seven days after inoculation of strain, pocks lesions occurred as 0.5-2.5mm diameter in size with grayish-white color and evaluated macroscopically and microscopically. At the histopathological examination, intracytoplasmic inclusion bodies and ballooning degeneration were detected in the hyperplastic and hypertrophic epithelial cells. Positive immunoreactions were also seen in the cytoplasm of the proliferative epithelial cells which may be reflected matrix inclusion bodies that is early form of inclusion bodies and not seen in histopathologically, but seen in ultrastructural examination. Numerous matrix inclusions which consist of developmental stage of virus were detected in effected cells by electron microscopic examination. As a result, this study indicated that, immunoperoxidase technique may be use in the morphologic diagnosis of early stage of the fowl poxvirus (FVP) infection.