This paper attempts to explain knowledge production in Swedish functional regions as measured by the number of patent applications. Recognizing that technological opportunity differs across sectors, a sectoral analysis is conducted. The Knowledge Production Function (KPF) approach is applied in order to relate patent applications to a number of relevant knowledge sources. The empirical analysis makes use of an aggregate KPF for each sector and region. In the interpretation of the results, the recent critique of KPF approaches is recognized. The stock of patent applications is included as an explanatory variable in the analysis. The results show that the patent stock of a region contains much of the information needed in order to explain current patenting activity. This is interpreted as suggesting strong effects of path dependence.