This report presents the highlights of what has been ascertained about the interactions of liquid and vapor sodium, NaK potassium, lithium, and cesium with solid materials of potential use in practical liquid-metal systems. Data for inclusion were selected by the authors on the basis of their practical utility to designers and research workers. There has been an accelerating interest in alkali metals as (1) coolants for fast-breeder nuclear reactors, (2) coolants in space power plants, (3) Rankine-cycle working fluids in high- temperature nuclear reactors, (4) propellants in ion-propulsion engines, (5) seeding materials in magnetohydrodynamic generators, (6) space-charge dissipating media in thermionic generators, and (7) high-temperature hydraulic fluids. Prominent among the liquid-metals research efforts are studies directed toward finding the best containment material for a given alkali under a given set of operating conditions.