Twenty-seven lots of standard immunoglobulin from 5 different producers and 18 lots of specific immunoglobulin (non anti-Hepatitis B) were titrated by RIA test for anti-HBs content. The highest titre in lots of standard IG (1:40) was lower than the lowest titre of the lots of specific IG (non anti-Hepatitis B) (1:44). The difference between means (1:17 and 1:42) was statistically significant (p less then 0,01). The reasons for the difference are discussed.