The effect of NO and O-2 concentration (as well as temperature) on NOX storage on a Lean NOX Trap (LNT) has been investigated using NOX breakthrough curves measured with a laboratory reactor. Data were measured over a wide range of temperatures (125-450 degrees C) and NO and O-2 concentrations. The break-through curves were run until the LNT was saturated to (i) enable NO oxidation to NO2 to be studied in the absence of NOX storage, (ii) to enable the effective NOX storage capacity as a function of temperature and concentration to be determined, and (iii) to provide a more demanding test for potential models. Under the range of conditions investigated, the amount of NOX stored at saturation was found to increase with NOX concentration, but to only be slightly influenced by O-2 concentration. The rate of NOX storage was found to increase with NOX and O-2 concentration. The data has been modelled and the performance of a number of kinetic models for NOX storage compared. It is shown that models which give comparable predictions over a narrow range of conditions can give different predictions when a wider range of conditions is considered; this demonstrates the importance of testing models over a wide range of conditions. Two types of storage sites were required to model the data: "Fast" sites are responsible for the initial part of the breakthrough curve, which is independent of temperature; both the rate of storage on these sites and the available capacity is independent of temperature. The rate of storage on "slow" sites, on the other hand, is temperature dependant, as is the available storage capacity. Slow sites are more abundant than fast sites. The rate of storage and the available capacity of both types of site are concentration dependent. (C) 2017 Elsevier Ltd. All rights reserved.