One approach to evaluating research and development investment, the historical tracing method, traces interrelated events over time to assess if and how R&D has spawned downstream developments of commercial or other interest. Recently the authors have added to the body of evaluative studies using this method by conducting five historical tracing studies for the US Department of Energy's Energy Efficiency and Renewable Energy Office. This paper draws on the five studies to illustrate the value of using a combination of tracing techniques. The value is in not missing critical linkages between R&D and outcomes, and in providing multiple lines of evidence of linkage. This paper highlights the value of patent citation analysis in providing objective, quantitative evidence of linkages that is developed in a non-intrusive manner. The discussion may provide useful insights to program managers and researchers considering the use of the method for evaluating R&D programs. Copyright , Beech Tree Publishing.