The present study was undertaken to perform an inventory of pig production systems, at farm level. The main aim was to document the variety of existing production systems in European countries. Information was collected from available sources, mostly national experts and literature, regarding target markets and information management, apparent degree of intensification, technical and economic performance, environmental impact and animal welfare. Eighty-four production systems were identified in 23 countries, of which 40 were reported as conventional and the remaining 44 were reported as differentiated. The differentiated and conventional production systems differ significantly in many respects; however, high variability was also found within each category as well as a large overlap between the two categories with respect to the distribution of most variables. Most differentiated systems claim to have superior characteristics in at least one dimension of sustainability. The specificities of these claims were analysed and multiple correspondence analysis of the data again showed considerable overlap between conventional and differentiated systems. Hierarchical clustering analysis resulted in three clusters. Systems in Cluster A (mostly conventional) have the characteristics of intensive production oriented towards standard quality. Systems in Cluster C (all differentiated) are just the opposite with numerous characteristics indicative of more extensive and more welfare- and quality-oriented production. Systems in Cluster B (made up of almost equal numbers of conventional and differentiated systems) fall between these two extremes; they are particularly common in Scandinavian countries and the Netherlands.