Combined IgA and IgG2 deficiency is well recognized as being associated with an increased susceptibility to pyogenic infection. A similar syndrome is described in four patients with IgA deficiency who were unable to produce IgG2 subclass antibodies to pneumococcal capsular polysaccharides but whose total IgG2 levels were in the normal or near normal range. This emphasizes the importance of measuring class and subclass responses to different types of antigen when investigating patients with suspected deficiencies of antibody production.