Voluntary standard setting organizations (SSOs) are a common feature of systems industries, where firms supply inter-operable components for a shared technology platform. These institutions promote coordinated innovation by providing a forum for collective decision-making and a potential solution to the problem of fragmented and overlapping intellectual property rights. This paper examines the economic and technological significance of SSOs by analyzing the flow of citations to a sample of U.S. patents disclosed during the standard-setting process. Our main results show that the age distribution of SSO patent citations is shifted towards later years (relative to an average patent), and that citations increase substantially following standardization. These results suggest that SSOs identify promising technologies and influence their subsequent adoption.