We use Fresnel zone plates as focusing optics in hard x-ray microprobes at energies typically between 6 and 30 keV. While a spatial resolution close to 0.1 μm can currently be achieved, highest spatial resolution is obtained only at reduced diffraction efficiency due to manufacturing limitations with respect to the aspect ratios of zone plates. To increase the effective thickness of zone plates, we are stacking several identical zone plates on-axis in close proximity. If the zone plates are aligned laterally to within better than an outermost zone width and longitudinally within the optical near-field, they form a single optical element of larger effective thickness and improved efficiency and reduced background from undiffracted radiation. This allows us both to use zone plates of moderate outermost zone width at energies of 30 keV and above, as well as to increase the efficiency of zone plates with small outermost zone widths particularly for the energy range of 6 - 15 keV.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.