In this study, polyacrylamide gel (PAG) dosimetry is used to quantitatively assess the efficiency of radiation sensitizers. The local dose enhancement caused by the K-edge absorption of certain atoms such as bromine and iodine can be employed to increase the damage to neighboring molecules and cells. Clonogenic assays can assess the radiation survival of cells to evaluate the efficiency of radiation sensitizers, but this technique requires reliable cell growth in culture media and is time consuming. Our purpose is to use PAG dosimetry to investigate the sensitizing potential of radiation sensitizers such as iodinated compounds. Incorporation of iodinated radiation sensitizers such as NaI and an iodinated contrast agent leads to a quantifiable dose enhancement ratio. When irradiated at low energy (approximately 40 keV), the dose enhancement ratio of the iodinated contrast agent at concentrations of 0.01 (3.5 mg ml(-1)), 0.05 (6 mg ml(-1)) and 0.1 (12 mg ml(-1)) M are 1.16 +/- 0.02, 1.39 +/- 0.03 and 1.82 +/- 0.04, respectively. No dose enhancement was observed when the samples were irradiated with 1.25 MeV gamma photons.