As many as 100 children aged 3 months to 4 years with lymphaticohypoplastic diathesis (LHD) were examined for clinico-immunologic++ interrelations. The children suffering from manifest LHD demonstrated the reduction of the amount of circulating T lymphocytes and IgA, IgM and IgG subpopulations. At the same time the changes in local immunity correlating with enlargement of the thymus and lymphoid formations in the nasopharynx were identified. The immunity unbalance in LHD was supported by morphologic and immunologic studies of the tissue of the removed hypertrophied tonsils. The specification of the deranged mechanisms of immunity in LHD requires early diagnosis of the illness, screening of the methods for immunocorrection and closer follow-up of the sick children.