This paper discusses the theory of a possible method of synchrocyclotron beam deflection in which the orbits expand until the point of maximumHr(n=1) is reached, after which the ions escape and spiral outward. These spirals should have a uniform starting radius and a small pitch in order to give deflection efficiency of the order of 100 percent; it is shown that this requires a flat maximum ofHratn=1, and small amplitude of radial oscillation. The radial and vertical oscillations of the beam and the couplings thereof are discussed in detail. It appears that the only field inhomogeneities which must be carefully minimized are those atn=1 andn=0. Limits on radial and vertical oscillations in the immediate vicinity of the ion source are set but the origins thereof in phenomena other than field inhomogeneity are not discussed.