The aim of this paper was to give a concise review of important poultry viruses with oncogenic properties. Depending on whether the etiologic agent is known, neoplasms of poultry are divided into virus-induced neoplasms and neoplasms of unknown etiology. There are three, economically important, virus-induced neoplastic diseases of poultry: Marek’s disease (MD), caused by herpesvirus, avian leukosis/sarcoma (ALS) and reticuloendotheliosis (RE), both caused by retroviruses. Although these neoplastic diseases cause economic losses from tumor mortality and poor performance, some have also served as highly suitable models to study pathogenesis of neoplasia. Lymphoid leukosis is a disease of poultry caused by avian leukosis virus (ALV). The disease is characterized by development of B-cell lymphoma in chickens aged approximately 16 weeks and older. Standard criteria used for diagnosis include disease history, clinical signs, gross necropsy and histopathology. There is no treatment nor vaccine available, so eradication of the virus from breeding flocks is the most effective control method.