Solid-liquid equilibria in the System L-leucine + L-valine + water have been measured at 298 K and ambient pressure. The system was shown to form solid solutions at equilibrium. The data also showed that the equilibrium composition Of L-leucine in the liquid phase was only slightly affected by the presence Of L-valine; whereas, the equilibrium composition Of L-valine increased significantly with the addition of L-leucine. A simple thermodynamic model was used to correlate binary L-leucine + water and L-valine + water solubility data, and then to estimate nonidealities in the solid phase in the ternary system. Surprisingly, the solid solution exhibited significant nonidealities, emphasizing the need for analysis of the solid phase when ternary solubilities are measured. (c) 2004 Elsevier B.V. All rights reserved.