This experiment was carried out to evaluate the immunological effects of Hwanhonsan extract. Hwanhonsan administration into mice enhanced Arthus reaction and DTH to sheep erythrocytes, and NK cells activities. Hwanhonsan extract augmented the DNA synthesis of mitogen-activated lymphocytes. Hwanhonsan also stimulated leucocyte migration ability, MIF and IL-2 production of T lymphocytes, but not IL-6 production of B cells. These results suggested that effect of Hwanhonsan might be chiefly due to nonspecific enhancement of NK cell activities and cell mediated immune responses.