This article examines the social structure of Argentina's main conurbation, Greater Buenos Aires, over the past four decades. The research focused on identifying changes in society by stratifying it into three social classes: high, middle and low. Contributions are made in three areas. First, the article engages with the renewed debates about methodology on the issue of which criteria are best suited to achieving an adequate demarcation of social classes, especially the middle class. Second, it uses a variety of approaches to document changes in the social structure with a view to identifying common trends. Lastly, it highlights certain dominant features of the workings of the labour market that appear to have left their mark on the social morphology of Argentina.