The authors investigated the eventual influence of gammaglobulin administration on the results of hemagglutination - inhibition test for the diagnosis of rubella. Single doses of 20 ml were injected intramuscvlary in 12 women. Evahiations carried out 15 and 30 days thereafter did not disclose any changes in the antibodies content in relation to those previously detected, presenting findings of interest from the practical standpoint since they will aid serologic tests emiluation every time that, as a preventive measure, gamniaglobulin was used for various reasons, chiefly for protection of pregnant women.