There is an ever increasing demand for cleaner steels, that is, those with low non-metallic inclusion content. This demand has driven research into improving our knowledge of reactivity of inclusions in liquid steel. In this study, spinel (MgAl2O4) inclusions of known composition/ phase and size distribution where added to the liquid steel bath prior to assessing their reactivity. The pO2 of the gas phase was controlled to 10-13 atm throughout the experiment. The inclusions were then tracked for changes in size, morphology and composition with time in an aluminium killed steel at 1600°C. It was found that the Mg:Al mass% ratio of the inclusions changed from -0.5 to 0.08. There was little change in the size of the spinel inclusions during the reaction. Full details of changes in Mg:Al mass% ratio, size and distribution of inclusions are reported and discussed. Copyright © 2013 MS&T'13®.