  We prove a dispersive estimate for the evolution of Schroedinger operators H
= -\Delta + V(x) in three dimensions. The potential should belong to the
closure of bounded compactly-supported functions with respect to the golbal
Kato norm. Some additional spectral conditions are imposed, namely that no
resonances or eigenfunctions of H exist anywhere on the positive half-line. The
proof is an application of a new version of Wiener's L^1 inversion theorem.
