The HPLC system separated completely isofavonoids such as daidzein (15.2 min) and genistein (17.3 min). Initially, the concentrations of major isoflavone Genistein and Daidzein in the tested soy milk were determined. Commercial soy milk samples were analyzed for isoflavones and two major isoflavones detected: genistein 25.86 (mg L-1) ±0.66 SD and daidzein 8.25 (mg L -1) ±1.13 SD. Concentrations of genistein in soy milk were higher than daidzein. The results obtained in this study can serve as a basis for estimating amount of soy milk can be consumed by people as related to its main isoflavone content. © 2008 Asian Network for Scientific Information.