A scanning microwave microscope (SmuM) for combinatorial characterization of dielectric materials has been developed using a lumped-constant resonator probe. The probe consists of a commercially available microwave oscillator module equipped with a thin conducting needle and an outer conductor ring. The capacitance between needle and ring changes with the dielectric constant of the sample just beneath the needle, which can be detected as a frequency shift of the resonator with high accuracy. The frequency shift values measured for various standard samples lay on a master curve theoretically predicted, which guarantees the quantitative evaluation of the dielectric constant. Applicability of the present system to the characterization of combinatorial samples is demonstrated. (C) 2002 Elsevier Science B.V. All rights reserved.