Diabetes is often identified as a risk factor for infections. We were interested in investigating the effect of “Ongael” on immunosuppressive diabetic mice. Ongael [leaves of Phaleria cumingii (Meisn.) F. Vill.] is used as a panacea for traditional treatment of many kinds of diseases in Palau. On the production of cytokine in the spleen from BKS. Cg-+Leprdb/+Leprdb mice, an animal model of non-insulin-dependent diabetes mellitus, oral administration of the 50% ethanolic extract (ONG-ext, 500 mg/kg) of Ongael significantly increased the production of interferon (IFN)-γ compared to that of vehicle control group. Mangiferin (100 mg/kg, p.o.), a major constituent of ONG-ext, significantly enhanced secretion of IFN-γ, tumor necrosis factor (TNF)-α and interleukin (IL)-2 compared to that of vehicle control group. These results suggest that Ongael acts as an immunopotentiator to immunoincompentence in diabetes mellitus. © 2006, Medical and Pharmaceutical Society for WAKAN-YAKU. All rights reserved.