Decisions to allocate resources in health care are increasingly influenced by relative cost effectiveness. To warn decision makers of some of the pitfalls currently found in cost effectiveness league tables and to suggest how meaningful comparisons may be made between health care technologies a published league table was scrutinised by examining its sources. This showed some of the methodological problems surrounding such tables and how such difficulties could be reduced in future. The source studies in the table featured different years of origin, discount rates, health state evaluations, settings, and types of comparison programmes; all of these differences may raise problems for meaningful comparison. Decision makers need to assess the relative value for money of competing health care interventions. In the absence of systematic comparisons such assessments are likely to take place informally. This will probably have a worse risk-benefit trade off than the formalized use of league tables.