Estimation of on-farm benefits is highlighted as a critical but complex issue in research evaluation. We identify many different potential impacts of research, many of which• do not fit into the standard supply-shift framework for research evaluation. Given the difficulty and complexity of benefit estimation, we see a renewed role for farm-level economic models (such as whole-farm linear programming model) in this area. The benefits of undertaking a more sophisticated and detailed analysis to estimate research benefits include not just greater accuracy but also greater credibility with researchers and greater relevance through representing factors which they perceive to be important. We discuss how, if such respect is engendered, a formal research evaluation this can yield additional benefits by improving the design and conduct of research.