This paper describes the design, assembly, and operation of a photoelectrochemical (PEC) test cell that is relatively easy to construct and well suited for testing photoelectrode/counterelectrode combinations in a reproducible manner. The design of the cell permits measurements to be made in both two-electrode and three-electrode arrangements. The benefits of conducting both two-electrode and three-electrode measurements are illustrated using data obtained from the new test cell for a PEC system based on a polysulfide electrolyte, CdSe0.8Te0.2 photoanode, and tungsten monocarbide counterelectrode. It is shown that linear sweep voltammograms measured in three-electrode mode can be used to describe current transients recorded in a two-electrode cell modified by the addition of a reference electrode.