A process and related system is disclosed for etching copper with, and regenerating, a working alkaline ammoniacal etchant solution, the regeneration involving withdrawal of a portion of the working solution as spent etchant solution and electrolytic removal therefrom of at least a portion of the etched copper therein so as to produce a fresh etchant solution which is returned to the working solution; accumulation vessels upstream and downstream of the electrolytic process; and supply to the working solution and/or the fresh etchant solution of sufficient oxygen and ammonia to maintain the desired cupric ion content and pH in the working solution.