Transparent conducting oxide (TCO) nanoparticles based on zinc oxide doped with aluminium and gallium (Al- and Ga-co-doped ZnO, AGZO) were synthesized using a continuous hydrothermal flow synthesis (CHFS) reactor by rapid hydrolysis and dehydration of aqueous metal salt precursors, in the presence of formic acid as an in-process reducing agent. The as-synthesised powders were characterized by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The as-synthesised powders were pressed into ceramic compacts and heat-treatment to ensure phase-pure wurtzite structure. The electrical properties of the materials were evaluated by Hall Probe measurements on the compacts, showing resistivities as low as 455×10-2 Ω cm, which represents a very high conductivity for a pressed disc based on ZnO. Copyright © 2016 American Scientific PublishersAll rights reserved.