Avianpox is a highly contagious disease infecting both commercial and wild birds, causing great damages to breeders and breeding. Caused by DNA viruses of the family Poxviridae, genus Avipoxvirus, if manifest through 3 forms, cutaneous, diphtheric and septicemic. In June 2003, during illegal commercialization of Brazilian birds, 800 wild birds (Paroaria dominicana, Sporophila caerulescens and Sporophila albogularis) were apprehended and being forwarded to the CRAS (Wild Animals Recovery Center), Tietê Ecological Park. After one month, birds presented cutaneous lesions in the beak and feet and anorexia, emaciation, locomotion difficulties, diarrhea, dehydration and death. Among the 800 birds, 500 died and 40 these (15 Paroaria dominicana, 15 Sporophila caerulescens and 10 Sporophila albogularis) were sent to the Electron Microscopy Laboratory of the Biology Institute of São Paulo, SP, to investigate viral agents. Scabs and fragments of skin lesions collected of theses birds were processed for transmission electron microscopy utilizing negative staining (rapid preparation), resin embedding and immunocitochemistry techniques. Under the transmission electron microscopy in all the analyzed samples it was visualized two types of poxvirus particles, M form, with regular spaced thread-like ridges comprising the exposed surface, measuring 280 x 230 nm; C form or stain-penetrated particle showing the dumbbell-shaped core surrounded by the outer envelope, measuring 360 x 330 nm. In the ultrathin sections obtained, three types of intracytoplasmic inclusion bodies were encountered: type A or Bollinger body, outlined by membrane, containing in its interior a great number of mature particles, measuring 200 x 300 nm, revealing the inner dumbbell-shaped core, two lateral bodies and an external envelope. In the type B electron dense inclusions bodies, viral particles budding of dense amorphous material were observed. Fibrillar inclusions constituted by groups of fibrils or lamellae were disposed in groups witch vary from 2 up to 5 e sometimes showed cross striations. A great number of vesicles, on the average measuring 1000 x 650 nm, containing in its interior granular material were also visualized. The nuclei were deformed and showed a marginalized chromatin. In the immunocytochemistry technique, the antigen-antibody was strongly enhanced by the dense gold particles over the viruses.