This article presents a meta-analysis of transaction cost theory, synthesizing and evaluating empirical research on organizational boundary decisions (make, buy, or ally). The study uses meta-analytic techniques to assess the validity of transaction cost theory, which posits that firms choose governance structures based on the relative efficiency of markets and hierarchies. The authors found strong support for the theory in both make versus buy and ally versus buy decisions. However, they did not find evidence that asset specificity has a stronger predictive power than uncertainty. Hierarchical and relational governance were found to align appropriately with transaction dimensions, leading to enhanced performance. The meta-analysis also addressed the normative implications of transaction cost theory, testing hypotheses related to the relationship between governance choice and performance. The results support the theory's predictions, indicating that hierarchical and relational governance choices can lead to better performance when aligned with transaction dimensions. The study contributes to the literature by providing a quantitative synthesis of a broad and diverse body of research, addressing issues of depth and breadth in transaction cost theory.This article presents a meta-analysis of transaction cost theory, synthesizing and evaluating empirical research on organizational boundary decisions (make, buy, or ally). The study uses meta-analytic techniques to assess the validity of transaction cost theory, which posits that firms choose governance structures based on the relative efficiency of markets and hierarchies. The authors found strong support for the theory in both make versus buy and ally versus buy decisions. However, they did not find evidence that asset specificity has a stronger predictive power than uncertainty. Hierarchical and relational governance were found to align appropriately with transaction dimensions, leading to enhanced performance. The meta-analysis also addressed the normative implications of transaction cost theory, testing hypotheses related to the relationship between governance choice and performance. The results support the theory's predictions, indicating that hierarchical and relational governance choices can lead to better performance when aligned with transaction dimensions. The study contributes to the literature by providing a quantitative synthesis of a broad and diverse body of research, addressing issues of depth and breadth in transaction cost theory.