This article examines the effects of the structure of intermunicipal cooperatives (IMCs) on the perceived transaction costs and benefits of IMCs. Hypotheses based on a polycentric theory of regional governance are tested using data from Dutch municipalities. The findings are mixed. In line with polycentric theory, networks characterized by a multiplicity of territorial scales reduce IMC transaction costs. Contrary to polycentric theory, however, if IMCs are organized under a uniform legal regime, lower costs and higher benefits are reported. Structural factors that dominate the debate between polycentrism and monocentrism prove to be of limited importance. On the other hand, the results indicate support for the hypotheses that intermunicipal trust (as a cultural variable) contributes to perceptions of effective and efficient cooperation.