The kinetics of diffusion-controlled aggregation of Frenkel defects(interstitial atoms and vacancies) under ii-radiation of solids is studied on a microscopic level. The theory is based on the discrete-lattice formalism for the single defect densities (concentrations) and coupled joint densities of similar and dissimilar defects treated in terms of the Kirkwood superposition approximation. The physical model takes into account random defect creation, diffusion, attraction and bimolecular, A + B --> 0 recombination. Conditions of the efficient aggregation of vacancies and interstitials are studied. The cooperative character of the aggregation process is shown.