Introduction/Objective: To determine how many planned purchasing and policy decisions made by a health authority in one year, could be based on evidence of effectiveness.

Methods: Descriptive study (1997/8) from one UK Purchasing Health Authority. (i) All decisions made in one year identified from health authority documents. (ii) Decisions classified by origin (eg government or local policy, or from commissioning GPs, other local professionals or consumers). (iii) Questions on the evidence effectiveness of each decision formulated. (iv) Search for evidence supporting decisions using an agreed search strategy. Main Outcome Measures: Proportion of decisions based on i) good systematic reviews or randomised control trials, ii) convincing non-experimental evidence and iii), without substantial evidence. Economic information also assessed.

Results/Discussion: 124 decisions were identified in one year. Only 20% of decisions could be readily supported with evidence from randomised controlled trials or systematic reviews. Even fewer decisions had sufficient economic data to support decision-making. Despite limitations in searching for evidence of effectiveness, a number of important health policy and commissioning decisions were identified where very little experimental or non-experiment evidence exists.