The main objective of this paper is to assess the role of a large set of factors which potentially relate agglomeration economies to local growth. Such a relationship is analysed thanks to an ample database on the case of Italy which refers to 784 Local Labour Systems and 34 sectors (21 manufacturing and 13 services) over the period 1991-2001. Econometric results show that local growth in Italy is characterized by significant differences across sectors. It is worth mentioning the positive influence of diversity externalities, human and social capital and the negative influence of specialisation externalities and competition. Spatial association is also detected.