From the text ... 'Over 1,900,000 acres (770,000 ha) of Yellowstone Park are managed as wilderness. The administrative policy for the management of natural areas of the National Park system such as Yellowstone clearly stated in 1970 The presence or absence of natural fire within a given habitat is recognized as one of the ecological factors contributing to the perpetuation of plants and animals native to that habitat. Fires in vegetation resulting from natural causes are recognized as natural phenomena and may be allowed to run their course when such burning will contribute to the accomplishment of approved vegetation and/or wildlife management objectives (U.S.D.I. National Park Service, 1970). Such a program was initiated in Yellowstone in 1972. This paper describes the implementation and 3 years results of this concept. Research procedures implemented are also described.The area considered for allowing naturally ignited fires to run their course met the following criteria: (1) The area should be managed as wilderness. (2) Natural fires occurring in the areas must not pose an immediate threat to primary visitor-use areas such as Old Faithful. (3) Human life must not be endangered under any circumstances. (4) Lands under the management of other agencies must be protected.'