Kinetics of nickel(II) extraction by 2-ethylhexanal oxime (EHO) has been investigated in a homothetic cell (Rushton cell) from ammonium solutions. The kinetic study was carried out with a stirring speed fast enough to eliminate the diffusion limitation. The chemical regime can then be assumed and the kinetic result can be used to determine the reaction mechanism. Thus, a kinetic mechanism has been suggested and a limiting step found. Influence of pH and the concentrations of NH4NO3 and EHO on rate have been investigated and results suggest that the limiting step is an interfacial reaction between a molecule of EHO monomer (HOx) and the adsorbed complex Ni(Ox)(H2O)(5ad)(+) (c) 2008 Elsevier B.V. All rights reserved.