Since the 1960s, Operations Research models have been applied to a range of healthcare problems. Despite the proliferation of papers in the academic literature, and individual anecdotal success stories, there are still major issues around getting OR models widely accepted and used as part of mainstream decision-making by clinicians, health managers and policy-makers. In this paper, focussing on simulation models, we discuss some of the possible reasons for this, briefly describe one successful implementation and suggest some potential ways forward.