The results o fan inquiry at the aggregate quarries of Piemonte, the Region ranking second in Italy as aggregate producer (about 20 million cu.m per year), are analysed in the paper. Data have been collected from a representative sample of both the alluvial and the massive rock exploitations, on excavation, washing, crushing and classifying machinery, on their efficiency, on manpower productivity. The sample has been divided into classes according to the yearly output level and features of the deposit, in order to calculate for each class average index values of the characteristic parameters of the production process: among them, the man shift productivity, the installed power per worker, the energy consumption per unit production, the installed power per unit production. A comparison can be so made between the different classes and types of production units, and the weak points in the production system can be pinpointed. In the concluding remarks, some suggestions are made on the evolutive trend of the aggregate production technology.