[en] Using average ¹³⁷Cs and ⁹⁰Sr concentrations in different water masses of the Baltic sea based on data given by various workers, values of the total amounts and the balances of these isotopes for the years 1960 to 1977 are presented. Results indicate that; the total content of ¹³⁷Cs reached its maximum value of 20 100 Ci in 1966, while the maximum content of ⁹⁰Sr, 20 600 Ci, was found one year later, the maximum difference between two interannual changes of the total nuclide contents found by two methods was +- 20% falr ¹³⁷Cs and +- 16% for ⁹⁰Sr, the maximum total contents of these two radionuclides were rather similar, and the effective half life was evaluated as about 9 years for ¹³⁷Cs and about 15 years for ⁹⁰Sr. (U.K.)