This research examines effects of supplying firms’ transaction specific investments on their firm performance through buyers’ trust and commitment. In this process, the research investigates moderating effects that buying firms’ purchasing strategies, which consist of relational strategy (competitive or cooperative purchasing strategy) and cost-reduction strategy (purchase price-based or total cost-based purchasing strategy), have on buyers’ commitment and suppliers’ performance. The study proposes a conceptual model integrating relationship marketing and purchasing strategy researches regarding business-to-business supplier-buyer relationships and test hypotheses derived from the conceptual model. Data were collected through a survey, and 248 purchasing managers participated in the survey.