For the evaluation of immunomodulatory effect of Korean Oldenlandiae Herb (OH) and Radix (OR), our experiment was performed with methanol extracts of Korean Oldenlandiae Herba and Radix. After administration of methanol extracts of Korean OH and OR for 7 days, Balb/C mice were immunized with sheep red blood cells. Four days later, splenic leukocytes were isolated and immunological experiments were performed. Rosette forming cells and plaque forming cells were significantly increased in Korean OH and OR treated mice compared with PBS treated control. Korean OH and OR also enhanced T and B lymphocytes, macrophage and natural killer cells by flowcytometric analysis. LPS-induced TNF-α and IL-6 levels were increased by OH and OR compared with untreated control. These results suggest that Korean OH and OR have immunomodulatory activity through regulation of cell-mediated immune and humoral immune response.