The report summarizes the results of the Baltic Sea radioactivity studies within 1981-1985 carried out by CMEA member-countries: DDR, PPR and the USSR. These studies were related to the impact from a number of Nuclear Power Plants located at the Baltic seashore. The distribution of strontium-90, cesium-137 and tritium concentrations across the Baltic Sea aquatory has been studied both in near-surface and deep water layers. The statistical analysis of the obtained data has revealed their normal distribution. The radionuclide contents were measured both in edible and non-edible parts of fishes and dose commitments due to internal irradiation related to the fish eating calculated for critical group as well as for general population. Both the found volumetric activities and evaluated dose commitments are 3-4 orders of magnitude lower than the permissible levels established by the regulations used in DDR, PPR and the USSR. The summarized statistical data and calculation results are presented in tables and graphics. Wide experience in the sea radioactivity studies has been acquired. 12 refs.; 22 tabs.; 15 figs.