Twenty-five weimaraners with recurrent infections or inflammatory disease were investigated; their median age was four months (range two to 36 months), and 11 of them were male and 14 female. Twenty of them showed signs of lethargy, anorexia or pyrexia, 13 had been vomiting or had diarrhoea, 12 had shown signs of pain in the joints or bones and been lame, five had had reactions at the site of an injection, five had generalised lymphadenopathy, three had urinary tract infections and two had recurrent or severe pyoderma. They all had a lower concentration of one or more classes of serum immunoglobulin (IgG, IgM and IgA) than the standard control ranges, and their mean concentration of IgG was significantly lower (P<0.005) than the mean concentration of IgG in 15 clinically normal weimaraners. Of 10 cases for which a complete vaccination history was available, nine had developed clinical signs within five days of being vaccinated. Follow-up data were available from 21 of the 25 dogs for a median period of 24.5 months. One dog died during a symptomatic episode, three were euthanased, six were alive at follow-up but had continued to show clinical signs and 11 had made a full recovery.