A new method has been developed for determining the composition of NiSn and PbSn alloys electrodeposited on a rotating disk electrode. The method makes use of a ring-disk assembly combined with potentiodynamic or galvanostatic stripping voltammetry. According to the method the alloy is first deposited on the disk electrode and.subsequently transferred to a stripping medium where it is anodically dissolved. During disk dissolution, Sn in the alloy dissolves in the +2 oxidation state and further oxidizes to Sn4+ on the ring electrode. The disk charge is proportional to the total amount of deposit while the ring charge is proportional to the total amount of Sn in the deposit. In addition to permitting composition determination, this method provides information about the phase structure of the electrodeposited alloy. © 1990, The Electrochemical Society, Inc. All rights reserved.