Abstract: A method and apparatus for disinfecting material such as a fluid stream, (e.g., water) or various objects (e.g., packaging, fruits, vegetables) using a high temperature expanding plasma emission source (EPES lamp) to generate intense pulses of ultraviolet light primarily in the 200-400 nm range. The EPES lamp is preferably mounted axially in a pipe through which the fluid to be disinfected is flowed or perpendicular to the direction of a fluid flow or an object conveyor. Each pulse is terminated before the resulting plasma within the EPES lamp reaches the inside surface of the EPES lamp wall so that the EPES lamp operates in an expanding plasma emission source mode rather than in a wall stabilized mode. The EPES lamp is operated at a plasma temperature of at least about 15,000.degree. K. and an energy density (Q) of at least about 300.