Dried whole blood of newborn infants on filter paper which is generally used for screening investigations for inborn errors of metabolism has been found suitable in a pilot study for demonstration of rubella antibodies. Investigation of 2522 newborn blood samples using the haemolysis-in-gel test showed lack of rubella specific antibodies of the IgG type in 236 cases. This indicates that 9.3% of mothers had no immunity against rubella. Inclusion of the test into existing newborn screening programmes would permit selective immunisations in the lying in period, discovery of rubella infections within the first months of pregnancy, and permit epidemiological studies. Financial and organisational requirements would be minimal. A considerable improvement in current rubella prophylaxis could thus be achieved.