Magnetic susceptibility measurements of anatase single crystals of TiO
2 are reported for the first time. The anatase single crystals behave
like a large gap semiconductor with a shallow donor level at 5 meV. Th
e susceptibility measured by ESR is due to electrons localized on the
donor state while the static susceptibility reveals the carriers therm
ally excited into the conduction band. The lattice contribution of the
susceptibility is dominated by a net Van Vleck paramagnetism surprisi
ngly lower in magnitude than in the rutile phase.