Since the late 1960s social policy scholarship has been concerned with the distribution of the resources or benefits across social gradients. This article presents a review of the literature on one mechanism by which inequity might be produced – activism by middle-class service-users enabling them to capture a disproportionate share of resources. The review used the methodology of realist synthesis to bring together evidence from the UK, the USA and Scandinavian countries over the past 30 years. The aim was to construct a ‘middle-theory’ to understand how and in which contexts collective and individual activity by middle-class service-users might produce inequitable resource allocation or rationing decisions that disproportionately benefit middle-class service-users. The article identifies four causal theories which nuance the view that it is the ‘sharp elbows’ of the middle-classes which confer advantage on this group. It shows how advantage accrues via the interplay between service-users, providers and the broader policy and social context.