A theoretical model of nanowire growth by the vapor-liquid-solid mechanism is considered, that accounts for the Gibbs-Thomson effect, the nucleation-mediated growth and the diffusion of adatoms to the wire top. It is shown that, within the range of growth conditions, the dependence of nanowire growth rate on its radius R is a quadratic function of 1/R. The coefficients of this dependence are obtained as functions of technologically controlled growth conditions. It is demonstrated that at sufficiently high surface temperatures, the growth is controlled by the direct impingement of material to the drop and wire growth rate that increases with increasing R due to the Gibbs-Thomson effect. When the temperature is decreased, the competition between the Gibbs-Thomson effect and the diffusion-induced contributions results in the length-radius curves with minima. Theoretical results are compared to available experimental data on the Au-assisted growth of GaAs wires by molecular beam epitaxy and good correlation is demonstrated between them. (c) 2007 Elsevier B.V. All rights reserved.