Gallium arsenide deposition rate studies were conducted with an open tube, chloride transport system which permitted independent control of the reactant input partial pressures. A recording microbalance was adapted to the deposition apparatus so that the epitaxial growth rates could be continuously measured during the actual deposition process. At low temperatures and high reactant partial pressures the process appears to be kinetically controlled. The rate then becomes inversely proportional to the gallium monochloride partial pressure and may indicate the presence of a competitive adsorption process. At high temperatures and low partial pressures the rates may be described in terms of a “quasi‐equilibrium” model where a fraction of the incoming gas stream equilibrates with the condensed phase.