The present study was concerned with a critical evaluation of common definitional concepts for the Proto- and early Aurignacian of Western Europe. Accordingly, the lithic production systems of assemblages of three sites, located in Northern Spain, have been studied. On the one hand, the assemblages of layers VII (Protoaurignacian), VI and V (both early Aurignacian) of Labeko Koba and layer IXb (early Aurignacian) of Ekain in the Spanish Basque Country have been chosen. On the other hand, the Proto-aurignacian layer H of the rock-shelter site of Arbreda in Catalonia has been considered. Especially the site of Labeko Koba promised interesting results, as assemblages ascribed to both postulated phases there occur in a stratigraphic succession.