The proportion of T-cell subsets was normal in all patients with X-linked agammaglobulinemia except for an 8-month patient who showed a decrease in OKT8+ T-cell population. In two patients with hypogammaglobulinemia with IgM production, T-cell subsets were normal in distribution and the patients' B cells produced only IgM in culture with autologous T cells. A patient with common variable immunodeficiency showed no imbalance in distribution of T-cell subsets. Imbalance of regulatory T-cell subsets was found in a patient with DiGeorge syndrome and severe combined immunodeficiency.