We describe the use of a near-field scanning microwave microscope to quantitatively image the dielectric permittivity and tunability of thin-film dielectric samples on a length scale of 1 μm. We demonstrate this technique with permittivity images and local hysteresis loops of a 370-nm-thick Ba0.6Sr0.4TiO3 thin film at 7.2 GHz. We also observe the role of annealing in the recovery of dielectric tunability in a damaged region of the thin film. We can measure changes in relative permittivity εr as small as 2 at εr = 500, and changes in dielectric tunability dεr/dV as small as 0.03 V-1. © 1999 American Institute of Physics.