This reflection on the context of the launching of Espaces & Sociétés in 1970 analyses both factors tied to the itinerary, thought and influence of its co-founder, Henri Lefebvre, and the impetus coming from other approaches to Marxist sociology. The genesis of the journal is thus interpreted as a moment of fragile convergence between these differing visions, in particularly around a definition of ‘urban’. In order to generate a dialogue with the other contributions in this special issue, the author also examines the different conceptions of ‘urban’ that have driven the journal’s history and the debates sparked by their successive definitions.