Because of the important applications of platinum alloys and related platinum-group-metals phases, complete phase diagrams for these systems are important for materials engineering. The currently accepted phase diagram for the Ag-Pt system is questionable because of its disagreement with earlier experiments and because of its claim for a lone ordered structure at 53%-Pt which was not characterized and which contradicts both computational predictions and analogy to the isoelectronic system Cu-Pt. A complete re-examination of the Ag-Pt system by computational and experimental means suggests a phase diagram similar to the isoelectronic system Cu-Pt. The unknown compound, claimed to be 53%-Pt, is found to be the L1(1) structure at 50%-Pt. (c) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.