By means of a unique longitudinal database with information on all industrial plants and employees in the Swedish economy, this article analyzes how geographic proximity influences the impact of spillovers and knowledge flows on the growth in productivity of plants. Concerning the effects of spillovers, it shows that the density of economic activities contributes mainly to the performance of plants within a short distance and that the composition of economic activities is more influential farther away. Regarding the influence of the local industrial setup, proximity increases the need to be located near different, but related, industries, whereas increased distance implies a greater effect of intraindustry spillovers. The analyses also demonstrate that knowledge flows via the mobility of skilled labor are primarily a subregional phenomenon. Only inflows of skills that are related to the existing knowledge base of plants and come from fewer than 50 kilometers away have a positive effect on the performance of plants. Concerning outflows of skills, the results indicate that it is less harmful for a dispatching plant if a former employee remains within the local economy rather than leaves it for a job in another part of the national economy.