Pilar is a city located in the third ring of the Buenos Aires metropolitan region (Argentina). Over the past 30 years, the widespread development of gated residential communities has seemingly gone hand-in-hand with an urbanisation of this outer suburb signalled by the arrival of new populations, enterprise, retail and other services. The growth of the ‘private city’ of these gated communities therefore has important implications for the ‘public city’ of the wider suburban municipality. Drawing upon original research based on the opinions of key informants, this paper considers how the growth of the ‘private city’ has contributed to the economy of, processes of community- building and social cohesion in Pilar. In conclusion, it is suggested that gated residential communities have been a major factor in the emergence of the dual suburb that is Pilar today.