The analysis of published and new data on a pulsed disinfection is presented. It allows the conclusion that the pulsed disinfection mechanism includes both germicidal action of UVC light and a rupture of bacteria due to thermal stress, caused primarily by all UV components of the light pulse. The role of simultaneous cooling and heating of bacteria during a flash lamp pulse has been estimated and a direct detection of such a mechanism is proposed. It is suggested that an optimum pulsed light source for disinfection must have as much percentile content of a broad UV spectrum and a high peak power as is technically justified. Two new applications for pharmaceutics and medicine are suggested.