  Superconducting SrTiO_{3-\delta} was obtained by annealing single crystalline
SrTiO_3 samples in ultra high vacuum. An analysis of the V(I) characteristics
revealed very small critical currents I_c which can be traced back to a
unavoidable doping inhomogeneity. R(T) curves were measured for a range of
magnetic fields B at I<<I_c, thereby probing only the sample regions with the
highest doping level. The resulting curves B_{c2}(T) show upward curvature,
both at small and strong doping. These results are discussed in the context of
bipolaronic and conventional superconductivity with Fermi surface anisotropy.
We conclude that the special superconducting properties of SrTiO_{3-\delta} can
be related to its Fermi surface and compare this finding with properties of the
recently discovered superconductor MgB_2.
