Newmont Mining Corporation has successfully applied online optimization to the low pressure, high temperature fluidized bed oxidation refractory ore roaster at their Carlin Property in Nevada, USA. This project has yielded significant benefits, including increasing gold recovery by two percentage points (2%) for refractory ore treated in this plant. This paper describes how online optimization was applied to the process, what benefits were realized, technical challenges involved and the key elements for this successful project. (c) 2005 Elsevier Ltd. All rights reserved.