We briefly review previous investigations of formation mechanisms of gas hydrates and then describe a variety of methodologies employed in molecular simulations of their crystal growth. A dynamic criterion for identification of solid and liquid-like molecules allows differentiation without the limitations of structural order parameters, with the fraction of molecules labeled incorrectly as low as 0.01%. We demonstrate that an interface detecting method based on an integration procedure can provide very good estimates of the interface positions. Results from simulations examining crystal growth behavior of CH4 and H2S hydrate are reported, including polycrystalline structures and annealing mechanisms. (C) 2010 Elsevier B. V. All rights reserved.