Eucommia ulmoides Oliver was tested to control the differentiation of cultured human mesenchymal stem cell into adipocyte. The extent of the inhibitory effect on the conversion of adipose was measured using Oil red 0 staining, which stains accumulated lipid droplets in the cytoplasm of adipocyte. The adipocyte differentiation was inhibited by an extract from E. ulmoides Oliver in the concentration range 0.01-50.0 g/l. After 2D PAGE, protein spots of E. ulmoides Oliver extract treated stem cells were analyzed. Several protein spots were strongly up-regulated in E. ulmoides Oliver extract treated cells. Among them, tropomyosin was identified by MALDI-TOF These results suggest that E. ulmoides Oliver has an inhibitory activity toward the adipose conversion, which is a major cause of obesity. (C) 2004 Elsevier Inc. All rights reserved.