Three-dimensional mapping of chain scission events following induced fracture in bulk polymer specimens is demonstrated. The mapping is accomplished by the addition of a profluorescent perylene diimide-based dye as well as a reference dye to the matrix. The profluorescent dye is a radical-reactive dye with a fluorescence intensity that increases significantly upon reaction with carbon-centered radicals. The presence of both dyes allows for a ratiometric determination of relative radical concentration that is essentially independent of phenomena associated with local non-fracture-related defects present in the bulk material. The method is demonstrated by mapping radical events along a scalpel incision in a polystyrene film as well as in a fractured polymer melt.