A non-occluded baculovirus was observed and purified from the hepatopancreas of juve-niles of Penaeus c hinensis with white spots on the carapace. The nucleic acid of thebaculovirus was demonstrated as DNA. The enveloped virion is a stocky rod-shaped particle and has a tail, which is an envelope extension. The nucleocapsid is a helical cylinder formed by two cap structures at both ends and 13 helical bands in the middle. One helical band is made up of 11 capsomeres formed by 3-row-parallel protein subunits. An ultrastructure model of nucleocapsid has been proposed. Viral morphogenesis begins in the nuclei and its process is composed of four stages: the formation of viral stroma, the formation of membrane, the assem-bly of viruses, and the formation of complete virions. Sometimes two or three nucleocapsids use one membrane to assemble during the viral assembly. This may result to: one membrane fragment envelops respectively each nucleocapsid so that two complete virions are formed each of which is one nucleocapsid in one envelope; or virions are formed, which are two or three nucleocapsids in one envelope.