The relative distribution of cells producing subclasses of IgG or IgA was examined by immunohistochemistry in lymph node biopsy specimens from 15 adults with persistent generalized lymphadenopathy due to infection with HIV and from 11 adults with lymph nodes enlarged from other causes. The IgG1 immunocyte fraction was significantly higher and the IgG2 fraction significantly lower associated with HIV infection than in the controls. The proportions of cells producing IgG3, IgG4, IgA I or IgA2 were similar in the two lymph node categories. The altered IgG-subclass distribution of immunocytes in HIV lymphadenopathy concorded with the serum levels that were significantly elevated for IgG1 and lowered for IgG2 compared with a panel of blood donor samples.