It has been shown that sectorial and zonary unhomogeneities of the crystal together with changing temperature conditions in the course of its growth are among the main causes of appearance of the structure defectiveness and property unhomogeneities in the volume of crystals grown. The method of rapid growing in the defined crystallographic direction [101] of the large-size KDP and DKDP single crystallites on the plain seed has been developed, which are applicable for production of wide aperture frequency multipliers of laser emission into the second/third harmonics (type II). Usage of such a method of growing allows to increase the coefficient of use of crystal material (KDP up to 40% and DKDP up to 70%) at production of nonlinear laser elements. High quality of the crystals grown has been confirmed by the results of investigation of structural perfection, optical homogeneity and bulk laser damage resistance threshold. (C) 2011 Elsevier B.V. All rights reserved.