There is wide acceptance that cost-effectiveness is a relevant consideration when deciding which treatments to make available in publicly funded health services. An unresolved issue concerns the timing and the extent of such evaluations. The United Kingdom provides examples of two distinct approaches. The Scottish Medicines Consortium (SMC) provides guidance to the NHS in Scotland based on a rapid early review of the evidence. The National Institute for Health and Clinical Excellence (NICE) provides guidance to the NHS in England and Wales based on a later, more extensive review of the evidence. This paper explores how the difference in approach affects the role of the pharmaceutical industry, clinical experts and other stakeholders. It compares the guidance produced when both bodies have evaluated the same medicines. It addresses the general question of when to assess the cost-effectiveness of medicines. It concludes that there are important differences between the approaches of SMC and NICE, relating primarily to the timing of the review of evidence on clinical and cost-effectiveness. The difference in timing means that the activities of the two bodies are to a large extent complementary.