Pedunculagin is an ellagitannin purified from Alnus hirsuta var. microphylla, Betulaceae. The effects of pedunculagin on the immune system have been characterized to induce enhancement of NK (natural killer) cell cytotoxicities against tumor cells. The present study investigated whether pedunculagin can enhance macrophage cytotoxicity against P8l5 tumor cells. Macrophage cultured with pedunculagin enhanced cytotoxicity in a dose dependent manner In addition, the same treatments increased NO production, which plays important roles in the immune system. liken together these results demonstrate that pedunculagin significantly enhances cytolytic activities of macrophage.