The application of results of basic research and of engineering principles to the solution of practical fire protection problems, but entailing, in its own right, research into fire phenomena and fire experience to provide an improved level of understanding of the nature of unwanted fire and its threat to life and property. The defense against destructive fire has been largely empirical and improvisational; although this approach has been reasonably effective in the past, it has not kept pace with urbanized and industrialized life. However, an impressive array of scientific and engineering disciplines has been brought to bear on the complex practical problems of fire defense. This article reviews the current state of fire technology, principally as it applies to urban fires.