Glucocorticoids are known to inhibit mitogen-induced proliferation of T cells by suppressing the production of interleukin-2 (IL-2). These hormones have also been shown to inhibit the production of other cytokines, namely IL-1 and interferon-gamma (IFN-gamma). It is demonstrated here that hydrocortisone is able to inhibit mitogen-induced production of human IL-4, both at the secreted protein, as well as at the mRNA level. This effect may explain, in part, the immunosuppressive effects of glucocorticoids in the treatment of allergic disease.