Abstract. The coupled system of the 3D hydrodynamical model THREETOX and the radiological box model POSEIDON-R, developed in the framework of the European system RODOS for emergency response to a nuclear accident, was applied to the Black Sea for reconstruction and outlook of the radionuclide contamination in result of bomb testing and the Chernobyl accident. For the model verification hydrophysical data was obtained from historical records of up to 15180 observational stations in the Black Sea. The data was grouped by months in l°byl° spatial squares and homogenised in the vertical with application of the method of Reininger and Ross. The radiological data was derived from literature sources mainly based on the expeditions of "Typhoon", IBSS, MHI, Hydrometeorological service (all from the former USSR), "K. Piri" and "Knorr" (US-Turkish) expeditions in the Black Sea. The vertical radionuclide stratification was obtained as one profile "mean for the whole sea" due to the scarce data. The spatial reconstruction of the hydrophyscal and radiological fields were done by gridding of the arbitrarily spaced data applying the method of "splines in tension" and eliminating aliasing by the median method. The THREETOX model was used for re-analysis of radionuclide transport. The 137 Cs concentrations calculated with POSEIDON-R in water and biota are compared with the collected data. A good agreement was found due to the implemented dynamic food chain model.