A method of repairing damaged hot refractory linings in high-temperature vessels includes forming an opening through the outer shell of the vessel proximate to the damaged region of the hot refractory lining, and introducing a refractory material into the damaged region. The refractory material is rapidly injected in a sufficient amount to effect complete filling, and is fast curing to strength at the operating temperature of the vessel. The method eliminates the need to allow the vessel to cool down to ambient temperature and then reheat the vessel to operating temperature thereby eliminating thermal cycling of the refractory lining.