A theoretical model of reversible reduction of amalgam forming ion on stationary mercury drop electrode is developed for square wave voltammetry. The dependence of dimensionless net peak current on the dimensionless inverse electrode radius is investigated. This relationship is not linear, but it is a curve with two asymptotes. These results apply to electroanalytical measurements at spherical microelectrodes. (C) 2014 Elsevier Ltd. All rights reserved.