Methods and compositions for high level disinfection (as herein defined) of a surface. Methods include treating the surface with a composition including a quaternary ammonium compound in a concentration which exceeds 1 % w/w and the temperature of treatment is in the range of from 30°C to 80°C. A log 6 reduction in Mycobacterium terrae is achieved on the surface in less than 10 minutes. The temperature may be produced by a physical chaotrope, a chemical chaotrope (such as) boron or a boron compound or complex or a combination of chaotropic agents. Sequestering agents and enzymes maybe added.
