Plans, prototypes, and initial test results for the charged‐particle beam (e−,e+) diagnostic systems on the injector rings, their transport lines, and the storage ring for the Advanced Photon Source (APS) are presented. The APS will be a synchrotron radiation user facility with one of the world’s brightest x‐ray sources in the 10‐keV to 100‐keV regime. Its 200‐MeV electron linac, 450‐MeV positron linac, positron accumulator ring, 7‐GeV booster synchrotron, 7‐GeV storage ring, and undulator test lines will also demand the development and demonstration of key particle‐beam characterization techniques over a wide range of parameter space. Some of these parameter values overlap or approach those projected for fourth generation light sources (linac‐driven FELs and high brightness storage rings) as described at a recent workshop. Initial results from the diagnostics prototypes on the linac test stand operating at 45‐MeV include current monitor data, beam loss monitor data, and video digitization using VME architecture.