Mercury metal dispersed spontaneously into the aqueous solution as micro-droplets when it came in quiescent contact with the solution. The self-dispersion was observed by means of the dynamic light scattering method, thermogravimetry and voltammetry. The mercury microdroplets generated in water had ca. 0.3 mu m in diameter. The diameter and the concentration of the droplets were stable. The concentration of mercury might be 1-3 mu mol dm(-3) if the droplets were to be dissolved homogeneously in water. The concentration exceeds the environmental limits by three orders of magnitude. The dispersed mercury was confirmed not to be ions or oxide of mercury but to be metal droplets. The self-dispersion of mercury belongs to the self-emulsification at liquidlliquid interfaces without surfactants. (C) 2012 Elsevier B.V. All rights reserved.