There is disclosed a process for coupling one or more different diazo components with resorcinol on an industrial scale. The process comprises adjusting and stabilizing the coupling pH of the resorcinol prior to the reaction with the aid of a buffer system and keeping it constant during the coupling reaction or reactions by controlling the ratio of flow of the streams of the diazo component or components and the base. The process makes it possible to prepare mono- and polyazo dyes in excellent uniform quality and yield.