Abstract: In order to study the morphogenesis and distribution of duck enteritis virus(DEV),tissues of ducks infected experimentally with DEV virulent strain were collected and observed by electron microscopy.The investigation showed that a few typical herpesvirus virions and nucleocapsids were observed in the spleen and bursa of Fabricius 12 hours post inoculation,then,in the liver,small intestine,spleen, thymus,bursa of Fabricius 24 hours post inoculation.Nucleocapsids are divided into four types according to their morphology. Nucleocapsids assembled both in nucleus and cytoplasm.There are two types of maturation according to our observation.One is nucleocapsids obtained its tegument in the nucleus and enveloped from the inner nuclear membrane.Another is nucleocapsids entered cytoplasm through nuclear membrane,then obtained their tegument in the cytoplasm,enveloped from the plasma membrane,finally released by necrosis,exocytosis or other ways.With the replication,assembly and maturation of viruses,inclusion bodies,compact particles, microtubes,hollow tubes and coated electron dense bodies are observed.