Experiments were undertaken to evaluate the effects of brazilin and hematoxylin on immune functions in normal young mice. Brazilin and hematoxylin decreased the circulating leucocyte counts. Brazilin and hematoxylin decreased the cirulating leucocyte counts. Both compounds did not produce a significant change of immunoorgan weights in comparison with those in the control group. Brazilin decreased significantly IgM plaque forming cells. Brazilin and hematoxylin decreased significantly Arthus reaction at 3 hours-post challenge with respect to aggregated bovine serum albumin.