A dielectric resonator filter including at least one microwave resonator having a cylindrical conductive cavity (1) symmetrically disposed about a longitudinal axis and an internally projecting flange (3); a cylindrical dielectric resonator element (4); and a ceramic support member (5) for the resonator element, the support member having a coefficient of thermal expansion to match that of the resonator element and being secured to the said internally projecting flange and adapted to support the resonator element in a spacial central position within the cavity whereby the longitudinal axes of the cavity and the resonator element are coaxial. The support member is in the form of a ceramic disc having a central aperture (6) within which the dielectric resonator is securely located at the periphery thereof, the shape of the aperture being such that the resonator element is secured to the support member at its low azimuthal field positions of the HEH IIδ mode.