1. The current method of providing cavitation safety of spillways based on the assumption of a limited amount of erosion developing during a prescribed repair period requires creating an absolute scale of cavitation erosion resistance of protective lining materials. 2. The traditionally used building materials (cement concrete, cement-sand mortars, wood, steel) and new building materials (latex concrete, polymer-sand mortars, polymer-concrete) make it possible to realize protective linings of spillways in various versions, and the spectrum of their cavitation erosion resistance can be selected in a quite wide range. 3. Cavitation erosion resistance of protective lining materials is their specific, special property which does not correlate uniquely with other properties and, in particular, with the indices of strength and abrasion resistance.