Abstract: A multi-ply radiation dosage indicator, and method of manufacture, is disclosed including a first ply having visible indicia thereon and a second ply having a radiation sensitive zone overlying the indicia of the first ply. The radiation sensitive zone is capable of changing opacity in response to exposure to a radiation dosage exceeding a predetermined threshold so as to change the visibility of the indicia thereby providing an indication as to whether the indicator has become irradiated. An optical filter ply may be provided overlying the indicia, and the indicator also may be provided with a transparent protective outer ply. A pressure sensitive adhesive ply having a removable release sheet is employed for attaching the indicator to a substrate.