We have observed giant Magnetoresistance (GMR) in Ni81Fe19/Ag granular structures synthesized by the annealing of artificial multilayers made by sputtering. The size and morphology of the magnetic precipitates can be controlled by adjusting the magnetic layer thickness in the initial stage. Magnetoresistance as large as 30% was found at 4.2 K with a rather small saturation field. Giant Magnetoresistance in this alloy system essentially depends on the magnetic precipitate size, annealing temperature and the Ni81Fe19 concentration. The temperature dependence of the magnetoresistance in these films is discussed.