Mutual solubilities of 21 nitriles in water have been measured from 0 to 90-degrees-C. All nitriles except malononitrile exhibited partial miscibility over this temperature range. Aromatic nitriles have higher solubilities than aliphatic nitriles, and an unsaturated nitrile (acrylonitrile) shows higher solubility than a saturated nitrile (propionitrile). In general, mutual solubilities decrease with an increase in the molar mass of the nitrile.