Influence of hydrogen on the growth of III-nitride materials by MOVPE is discussed using modeling and experimental study. The main conclusion, coming from the modeling and supported by numerous experimental observations, is that hydrogen affects the growth of III-nitrides in two different ways: via layer etching at elevated temperatures and via surface coverage with metal adatoms. The adatoms are found to accumulate on the surface due to interaction with hydrogen in a wide temperature range, including reduced temperatures. With regard to these effects, one can control such important characteristics as layer composition, growth anisotropies, surface quality, and even material properties (like p-doping level) by adjusting the carrier gas composition and other growth parameters. (C) 2008 Elsevier B.V. All rights reserved.