The problem to optimize the number and locations of environmental radiation monitoring detectors is formulated by taking the specifically defined distance measures ·as a performance index and solved numerically using heuristic programming such as branch and bound method. An ideal numerical example neglecting noises due to background radiation and so on shows that the desirable number and locations of detectors are detennined mainly by the atmospheric conditions and do not so influenced by the variation of the rate and pattern of activity release from the nuclear facility. It is shown also that the appropriate and sufficient number of monitoring--detectors to be located around the facility will be from three to six at most, if considered from the viewpoint of pattern recognition.