Simultaneous absence of the IgG1, IgG2, IgG4 and IgA1 immunoglobulins has been unambiguously demonstrated in a healthy 75-year-old woman by testing for allotypes, isoallotypes and for isotypes of these four subclasses. Only IgM, IgD, IgG3, IgA2 and IgE were present. The IgG3 levels were significantly increased. Family investigation showed inheritance of a haplotype Gm-;-;b A2m2. This person is homozygous for an extensive DNA deletion including the C gamma 1, C gamma 2, C gamma 4 and C alpha 1 genes.