Abstract: Process and apparatus for the dispersion and proportioning of fibers used in the building sector in general that consists of mechanical equipment equipped with feeding, stirring and proportioning systems, which may be operated electrically or hydraulically, applicable to both hot and cold bituminous mixes, having an air injection dispersion system, that may or may not be equipped with a vibrating motor with elastic joint between the hopper and the proportioning body. In the stirring and proportioning body there are two shafts, one of which is provided with blades to homogenize the fibers and the other one has a spindle independent from the first shaft, which rotates at a variable speed, the fiber-air blend passing through the dispersion tube which is smaller than the proportioning tube. The fiber mass is made to fall on some deflectors located at the disperser outlet and the assembly may be mounted in an immovable or movable manner.