The Davis-Greenstein theory for the orientation of interstellar grains is reconsidered. First the physical process of orientation is discussed from a different viewpoint, based on equilibrium considerations rather than on particle dynamics. (1) The Fokker-Planck equation is used to show that for spherical grains the distribution of rotational kinetic energy about an axis perpendicular to the magnetic field, B, corresponds to thermal equilibrium at a temperature between the gas kinetic temperature, Tg, and the internal grain temperature, Ti. The ratio, , of the diffusion coefficients due to magnetic dissipation and to atom-grain collisions determines the precise equilibrium temperature. The distribution of rotational energy about an axis parallel to B, for which magnetic dissipation vanishes, corresponds to thermal equilibrium at the gas temperature, Tg. If Tg exceeds Ti and is large, the rotational momentum, J, will tend to be oriented parallel to B. (2) Similar equilibrium arguments in the absence of a magnetic field show that the axis of symmetry of a rotating prolate spheroid tends to be perpendicular to J. These two results may be combined to give an approximate determination of the orientation, which agrees roughly, for weak orientation, with the value obtained from the Davis-Greenstein dynamical analysis. while the exact orientation has not been determined, the present point of view takes inverse reactions correctly into account, giving no orientation when Ti equals T0, and seems to provide a simple, more realistic physical picture. Second, the magnetic dissipation to be expected in different possible substances that might be present in interstellar grains is re-evaluated, using recent theories of the complex physical processes involved. For paramagnetic relaxation the imaginary part, ", of the magnetic susceptibility does not differ greatly from that adopted by Davis and Greenstein. For ferromagnetic single domains, however, a detailed analysis of rotational mode dissipation by ferrous ion impurities, following the model developed by Galt, yields a magnetic susceptibility that may exceed by factors of 106 or more the values previously assumed for interstellar ferromagnetic grains. For large, multi-domain grains the dissipation associated with domain wall motion gives about the same range under interstellar conditions as f?r single domains. If iron atoms in a grain are gathered in clumps of about 100 atoms each, the grain is super-paramagnetic" and " can be even greater than for a ferromagnetic grain. The values of B required for grain orientation with these ferromagnetic and super-paramagnetic grains are between 10-5 and 10-8 gauss. We conclude that orientation of interstellar grains in fields as low as 10- gauss seems a not-implausible expectation.