The geometric and electronic properties of alkali metals (Na and Cs) on ZnO(10-10) are investigated by means of photoelectron spectroscopy and low energy electron diffraction (LEED). Growth of the Na overlayer on ZnO(10-10) at room temperature is characterized by layer-by-layer growth or monolayer growth followed by three-dimensional cluster growth. The Na adatoms in the first layer are in a cationic state, and the metallic phase is formed on top of the first cationic layer. Although Na deposition at room temperature does not yield any long-range ordered superstructure, annealing the Na-covered surface results in a (1×3) LEED pattern, and we propose the formation of the Na atomic chains along the Zn--O dimer rows. For the Cs adsorption system, the disordered overlayer by ionized Cs adatoms is also formed throughout the submonolayer coverage region. Unlike the Na adsorption system, heat treatment of the Cs-covered surface does not yield any ordered structure until all Cs adatoms desorb from the surface. [DOI: 10.1380/ejssnt.2005.299]