This study is concerned with determinants of spatial concentration in both the manufacturing and service sectors in Sweden during the period 1975-93. By implementing a detailed data-set on the regional distribution of production, the study is addressed first to the degree of regional concentration in Sweden through Ellison-Glaeser indexes and regional Ginicoefficients. It is shown that concentration is considerably stronger in the manufacturing sector than in the service sector. Moreover, the differences have widened over time. In services, knowledge intensity seems to promote concentration to a larger extent than in manufacturing. An econometric examination is then conducted of the determinants of spatially concentrated industries in the manufacturing sector. Results indicate that production technology and the historical distribution of production seem to exert a stronger influence on location than non-pecuniary knowledge externalities. Finally, the degree of regional concentration in Sweden is compared with France and the USA. We find that concentration in production is more pronounced in Sweden than in these other countries.