The technique of adiabatic fast passage has been employed to measure within +/-1% the susceptibility of pure He3 and some He3--He4 mixtures for temperatures between 0.9°K and 3.0°K. Above 1.2°K the susceptibility varies as the inverse of the temperature, indicating that the statistical and exchange correction to the Curie susceptibility is very nearly constant. We have calculated the magnetization of an interacting system of He 3 particles near the classical limit. Plane waves have been used to evaluate the potential energy and the exchange energy of the particles. In this approximation potential correlation is handled by the introduction of a cutoff radius a. For reasonable choices of the cutoff, the statistical correction and the exchange correction are of comparable magnitude.