The in situ dissolution of polished (0001), (10 (1) over bar0), and (000 (1) over bar) surfaces of ZnO was studied using Atomic Force Microscopy under alkaline conditions. In aqueous NaOH solution the (0001) plane forms a stepped surface whereas the (000 (1) over bar) plane converts into more stable {10 (11) over bar} planes. Dissolution of the (10 (1) over bar0) plane leaves a combination of (0001) and (10 (11) over bar) planes. Dissolution in solutions containing both NaOH and Na(3)citrate causes the (0001) plane steps to increase in number and reduce in height, and cause an overall increase in the rate of dissolution in the < 10 (1) over bar0 > directions. These observations are explained using a mechanism based on edgewise dissolution where the etching rate depends on the number of surface oxygen atoms per zinc atom. Large areas of single index faces (over SO mu m(2)) of (0001) and (000 (1) over bar), suitable for surface chemistry studies, were also generated by chemical dissolution.