The results of studies on submicroscopic organization of nuclear polyhedrosis viruses (NPV) isolated from different species and populations of insects are presented. The following morphological criteria are proposed for NPV identification: the frequency of occurrence of polygenomic virions with definite number of nucleocapsids, the presence of electron-dense membrane on the surface of suprapolyvirion capsids (SPVC); total number of nucleocapsids inside one average SPVC of NPV. Analyses of morphometric maps of NPV infecting different species and populations of the same species of insects are presented.