Abstract: A method for monitoring the constituents present in an electroless plating bath solution. The method involves measuring ac spectra using a working electrode which has a high hydrogen overvoltage. First, a selected dc potential is applied to a working electrode which has been subjected to pretreatment and which is present in the electroless bath being analyzed. The electrode must have a high hydrogen overvoltage and is preferably an alloy of a low hydrogen overvoltage noble metal and a high overvoltage metal. A constant ac signal is superimposed on the dc potential. The dc potential is then swept over a chosen range at a selected sweep rate. The various constituents in the bath are then monitored by measuring the ac current at one or more reference phase angles with respect to the constant ac signal between the working electrode and a reference electrode as the dc potential is varied. The resulting ac spectra provides a useful measurement of the make-up of the constituents in the electroless plating solution.