The kinetics of growth of platelets on the pyramidal {10 (1) over bar1} and prismatic {1 0 (1) over bar 0} faces of zinc single crystals and the alteration with time.t of the edge length a of the {0 0 0 1} basal face of the same crystals in the presence of argon were investigated. The measurements of the edge a with time show that at the moment when the critical size ak is reached, the transition from kinetic to diffusion regimes starts. The comparison between the time when the visible platelets appeared on the zinc crystals and the a(2) vs t curves revealed that the first platelets grow exactly at the transition between the two regimes. It has been established that during the initial stage, when the size L is small, the platelets grow at a constant rate. During further growth, as the size L increases and reaches the critical dimension L-k, a change in the L-2 vs t curves appears: the linear curve is transformed into a parabolic one. In conformity with the morphological theory of Chernov in the isotropic case, it is concluded that the platelets grow in a kinetic and a diffusion regime. This effect of transition from the kinetic to the diffusion regime during the growth of platelets, similar to the effect observed during the growth of zinc single crystals, is a common phenomenon, which results from the diffusion conditions under which platelets and single crystals grow. (C) 2003 Elsevier Science B.V. All rights reserved.