The objectives of this paper are partly to add to the worldwide literature on contemporary levels of concentration – but in our case for a small island economy, and partly to provide a reference study which yields a concise and accessible source for anyone interested in gaining a quick picture of the state of concentration and diversification of the leading firms in Mauritius. In the main, we have confined ourselves to fact-finding at this stage, and the novelty of the work lies in the descriptive statistical framework within which it is presented. Nevertheless, it is inevitably policy relevant. In our opinion it suggests the need for continuing vigilance of concentration in individual markets, but also more research in the potential competition implications of the fact that the very largest firms have leading, possibly dominant, market shares in more than one industry – is such diversification a cause for competition concern?