Biological assessment of radiation exposure, or biodosimetry, is critical in suspected radiation exposures when physical dosimetry is not available or uncertain and is still necessary to confirm physical dose estimates. Accurate dose estimates are crucial in making life saving medical decisions for exposed persons, for determining other health consequences, or for reassuring non-exposed persons. the dicentric assay is the most documented method for biological dose assessment and is now an accredited method for biodosimetry. We have established the dicentric assay at FOI by developing and optimizing protocols for our laboratory. A dose response curve for low LET gamma radiation has been developed in vitro 137Cs irradiation of human lymphocytes. Our results are in good agreement with curves developed at other biodosimetry laboratories. Future efforts in the area of applied biodosimetry will be on developing methods such as fluorescence in situ hybridization, FISH, and premature chromosome condensation, PCC, that fill in the gaps of the dicentric assay.