The radiation environment of the Danube river has been studied from Bratislava city down to river mouth that is within the distance of 1869 km. Systematic measurements were carried out at 22 points in the territories of the USSR, Roumania, Bulgaria, Hungary and Czechoslovakia. Samples of water, sediments and aquatic organisms were used to determine such radionuclides as natural uranium, radium-226, potassium-40, tritium, strontium-90, cesium-137. In general the radiation environment of the Danube river can be considered as a function of the natural radionuclides presence and artificial radionuclides global fallout. No specific radionuclides from other sources were observed. Thus a conclusion can be drawn that the presence of operating Nuclear Power Plants in the Danube vally has no negative effects on its radiation environment. Measurements data of radionuclide concentrations are given. 7 refs.; 18 tabs.