This paper described the institutional functioning of commonly owned forests in Sweden. A total of 33 common forests were designated in 1861 and have been regulated by the same legislation ever since. Shares in the commons were determined by shares in local arable land and benefits to shareholders have included cash payments, private subsidies and local infrastructure. The common forests have competed successfully in timber production with large-scale timber companies, which the author ascribed to their low transaction costs. They also scored highly on three of five criteria of institutional performance. Overall, their success might be due to their efficient integration into, rather than separation from, the formal economy.