AbstractWhen lymphocytes are stimulated with mitogens or antigens they are enhanced via a cascade of lymphokines to produce interferon-y (IFN-y). IFN-y augments the H2O2secretion of human monocytes which indirectly can be measured by chemiluminescence. We tested prednisone, 16-methylen. prednisolone and ACTH for their effect to inhibit the Con-A induced stimulation of the chemiluminescence-activity. All three hormones inhibited significantly the stimulation: prednisone up to 52.5%(concentration = 150 m;g/ml, p=0.000005), 16-methylen-prednisolone up to 22.5%(concentration = 2.5&m g/ml, p=0.006) and ACTH up to 33%(concentration = 10 m g/ml, p=0.0036).