This study draws on transaction cost, resource dependence, and organizational learning theories to posit relationships between transaction performance and transaction structure (alliances versus acquisitions), interfirm synergies, and motives. The study involves analysis of 66 international and intranational alliances and acquisitions that were undertaken in the pharmaceutical industry. An initial survey was administered to firms involved in these transactions to gather information regarding motives, transaction structure, and interorganizational synergies. A second survey was administered two years after the transaction to gather information on transaction performance. Findings support the importance of transaction structure and strategic synergies between firms. Specifically, transaction structure and high levels of strategic fit between the firms had a positive impact on performance. There is also some evidence that synergies must be linked to the motives driving the transaction. The study yields meaningful results regarding factors leading to success of transactions (alliances and acquisitions) in a longitudinal study of intranational and international transactions in the biopharmaceutical industry.