Abstract: Genistein and daidzein are soybean derived isoflavones which exert various biological effects. The roles of these isoflavones in adipocyte metabolism have also been demonstrated. Our experiments aimed to explore the lipolytic regulating actions of both isoflavones in adipocytes derived from normal pellet diet (NPD)-fed rats and high fat diet (HFD)-fed rats. Adipocyte suspensions were prepared from epididymal fat pads of Sprague-Dawley rats using the collagenase digestion method. Isolated adipocytes were incubated with genistein or daidzein at concentrations of 0.01, 0.1 and 1 mM for an hour at 37 °C. In the NPD-group, genistein (0.1 and 1 mM) and daidzein (only at 1 mM) significantly increased basal lipolysis. Similar lipolytic-stimulating actions of genistein and daidzein were found in adipocytes derived from HFD-fed rats. Isoprenaline-induced lipolysis in the NPD-group was augmented by genistein (1 mM) and daidzein (0.1 and 1 mM). However, in the HFD-group only 0.1 mM genistein significantly increased isoprenaline-induced lipolysis whilst daidzein did not affect isoprenaline-induced lipolysis at any of the concentrations tested. In summary, daidzein and genistein induced a significant increase in basal lipolysis with similar actions in both the NPD-group and HFD-group. However, the isoprenaline-induced lipolytic responses to the isoflavones between these two groups were different. Generally, isoprenaline-treated adipocytes derived from HFD-fed rats were likely to be less responsive to the isoflavones. Further experiments should be performed to explore this difference.