The suitable choice of a substrate material is one of the aims to be fulfilled in high speed microwave technology. LaMgAl11O19 oxide ceramic material, which belongs to the magnetoplumbite family, has been reported earlier as a potential candidate for such applications. This material has been prepared by conventional solid-state ceramic route. The structure has been studied by X-ray diffraction and characterized at microwave frequencies. The effect of dopant and glass addition on the microwave dielectric properties of this material has also been investigated. LaMgAl11O19 has relatively low dielectric constant (epsilon(r) = 14), low dielectric loss or high quality factor (Q(u) x f > 28,000 GHz at 7 GHz) and small temperature variation of resonant frequency (tau(f) = - 12 ppm/degreesC) at room temperature (300 K). These properties make LaMgAl11O19 as a good substrate material and as a dielectric resonator to be used in microwave devices operating at relatively high frequencies. (C) 2002 Elsevier Science Ltd. All rights reserved.