Phase behavior of vitamins in aqueous solutions is important in chemical processing and medical and dietary applications. Solubility is reported for two fat-soluble vitamins, vitamin E (alpha-tocopherol) and vitamin K-3 (menadione), in aqueous mixtures containing ethanol at 33 degrees C. Both vitamins have very low solubility in pure water owing to hydrophobic repulsion. Addition of ethanol in the water results in a large increase in solubility, mostly due to nonpolar attractive interactions between ethanol and vitamin molecules. For example, by addition of 70 mass % ethanol, vitamin E solubility increases 450-fold and vitamin K3 solubility increases 170-fold. The enhancement is more pronounced with vitamin E because it is more hydrophobic than vitamin K-3.