The results obtained on using an adjuvant vaccine against enterotoxaemia caused by E. coli in suckling piglets are discussed on the basis of an inquiry conducted among a number of veterinary practitioners. The vaccine contains the OK groups O138:K81,K88, O141:K85ab and O149:K91,K88 and is administered parenterally to the dams during the latter half of gestation. The inquiry which covered 4,000 sows on fifty-five farms showed that, as regards diarrhoea during the first week of life, morbidity in the offspring of vaccinated sows decreased from 83 per cent to 6 per cent and that mortality dropped from 23 per cent to 0.3 per cent. Clinical results were slightly less satisfactory where diarrhoea during the second and third weeks of life was concerned. The importance of serological typing prior to vaccination is stressed. Abortion occurred in 0.5 per cent of the vaccinated sows within three days after vaccination. The question is raised whether there is a relationship between this vaccination and abortion.