Abstract GafChromic TM Dosimetry Media is a thin film containing a colourless radiochromic imaging layer which produces a high resolution blue image when exposed to ionizing radiation. The high resolution of this film makes it a good candidate for use in dose distribution mapping with high spatial resolution. The response of GafChromic TM Dosimetry Media over the dose range from 0.1 to 5 kGy was studied by Saylor et al., (1988). To permit the use of the film at the higher absorbed dose levels currently used in many radiation processes, studies were performed to extend the useful absorbed dose range up to 40 kGy. The GafChromic TM Dosimetry Media was found to offer ease of handling and high reproducibility. However, the radiation response is dependent on temperature and humidity. Post-irradiation colour formation is significant immediately following irradiation. A five hour stabilization period is advisable before the optical density is measured. For use in routine dosimetry, the dosimeters should be calibrated against a reference standard dosimeter under the conditions of use.