Abstract: Methods of detecting the presence of concealed weapons and determining the type of weapons with a greater degree of certainty and reliability. The method involves tagging of the weapon with a radioactive marking that produces penetrative radiation, and providing radiation detectors at entrances to commercial and private residences, airlines, vehicles and other places. According to a preferred method, the tagging or marking of the weapon is in a form of a digital coding; and a different common coding is applied to each different kind of weapon. For example, hand guns receive a common code of one type; knives a different code; explosives a third different code, and the like.