As part of a research program on the reinforcement of mine structures by injection of polymeric resins, a neutron radiographic method has been developed to map the flow of polymer in shale rock. The method was applied in the examination of rock samples from laboratory and mine tests where polymers were injected in rock fissures. Thin (<5 mil) polymer veins and layers up to a depth of in. in rock specimens could be conveniently detected by this method.