The void ordering under irradiation in simple cubic, bcc, fcc and hcp-crystals is considered within the framework of the dislocation mechanism of void lattice formation by Dubinko et al. The ordering criteria are derived taking into account the structure and density of interstitial dislocation loops and straight dislocation network. The derived dependence of void lattice parameter and stationary void size on the concentration of the loop nucleation sites show that impurity atoms are necessary in order to provide the unfaulted loop nucleation rate sufficient for the void ordering. 15 refs.; 2 figs.