The proposal concerns development of an electrolytic process for the on-line regeneration of acid cupric chloride etching baths. Chemical regeneration on a batch basis is generally practiced today, utilizing chlorine and/or hydrogen peroxide to re-oxidize the Cu+, formed by the etching process, back to Cul+. These processes suffer the disadvantage of resulting in a net increase in solution inventory which must be disposed. Strong environmental and cost incentives exist for development of an efficient electrolytic regeneration process. Phase I will comprise the construction and operation of a flow loop to demonstrate continuous etchant regeneration, maintaining steady state concentrations of CuC@ ' , CuCl and HCI, with avoidance of the parasitic electrochemical reactions of chlorine and hydrogen evolution. At the same time, cathodicauy generated copper metal will be extracted from the system, balancing that consumed in the etching process.