Corticosteroids are efficient in many kidney diseases but their use is commonly empirical. Their anti-inflammatory effects are often difficult to dissociate from their immunological effects. These consist in inhibiting lymphocyte proliferation without greatly affecting their cytotoxicity and antibody synthesis. Corticosteroids induce lymphopenia and influence the distribution of lymphocytes subpopulations. This leads to prevention of cells homing in target organ and markedly affects immunoregulation. This latter action may explain the beneficial effects of corticosteroids in diseases with profound disturbances in immunity.