Abstract. We consider the stability of plane wave solutions of both single and coupled complex Ginzburg-Landau equations and determine stability domains in the space of coefficients of the equations. [6,11] and the references therein).Actually, CGL equations describe the evolution of the amplitudes of unstable modes for any process exhibiting Hopf bifurcation, for which the continuous band of unstable wave numbers is taken into account. Therefore, the equations have become a self-significant object of study.Coupled CGL equations govern the amplitudes, on slow spatial and temporal scales, of traveling waves propagating in opposite directions on the faster temporal and spatial scales associated with the original problem from which the GinzburgLandau equations were derived. The case when one of the amplitudes equals zero corresponds to a traveling wave solution of the original problem, while the case when the moduli of the two amplitudes are equal corresponds to a standing wave.The simplest solutions of CGL equations are plane wave solutions and the present paper is devoted to an analysis of their stability. Stability of traveling wave solutions of a single CGL equation, which arises when the most unstable wave number is