Titer determinations of hepatitis B immunoglobulins, as performed for example with radioimmunoassays or with haemagglutination tests, always show wide deviations; if a reference preparation, on which the test results can be based, is not run simultaneously with the test, the results are not comparable. A simple and easily reproducible radioimmunological method is described: the regression line is calculated for the titer series of a reference preparation, whose end titer is established; the anti-HBs content of the preparations under test can then be compared.