Economic geography and regional planning suffer from a lack of clear answers with respect to the question what methods to use to systematically explain complex territorial phenomena such as regional development. Rather than the universal effect of causes, analysis should focus on patterns revealed through case-specific effects of enabling and disabling conditions. Using qualitative configurational analysis (QCA), this paper illustrates the relevance of such an approach examining the variable effectiveness of intermunicipal collaboration in the Netherlands. Drawing on a survey of a large sample of collaborations, complemented with case-specific inside knowledge, eight conditions are found supporting collaboration effectiveness: age, size, homogeneity, project/policy activity, mission and inclusiveness. The configurational analysis uncovers one dominant evolutionary pattern (evolving policy focus), one minor pattern (metropolitan collaboration) plus two somewhat unique cases. It also finds contributing roles for mission-orientation, inclusiveness, and, somewhat surprisingly, size. QCA proves a promising tool to study complex dynamics across a population of territorial cases.