Tracking and using data to inform decisions pays off for college success programs on multiple levels. Having data allows program staff to monitor the progress of individual students and tailor support to their particular needs. It enables staff to understand the effectiveness of program activities and make improvements as necessary. Most importantly, data tell staff, board members, and funders the impact of the organization's college success services on student outcomes and the degree to which the organization is successfully fulfilling its mission. This paper describes how five organizations participating in the Success Replication Project organized by the National College Attainment Network (NCAN) and funded by the Michael & Susan Dell Foundation track and use data to measure their effectiveness in helping students they served in high school earn a college degree. These organizations are: (1) Capital Partners For Education, Washington, D.C.; (2) DC Prep, PrepNext, Washington, D.C.; (3) Operation Jump Start, Long Beach, CA; (4) Project GRAD Houston, Houston, TX; and (5) Ready to Rise, Degrees of Change, Tacoma, WA. The paper discusses the types and sources of data to track, how organizations secure, compile, and analyze data, and the ways programs use data to inform decision-making. The paper concludes with a description of resources developed by NCAN to assist organizations with tracking and using data to improve student outcomes. [For the "Scaling Success Services" series overview paper, "Scaling Success Services: Strategies for Promoting Postsecondary Success," see ED612064.]