To appraise the quality of economic studies undertaken as part of evaluations of guideline implementation strategies, we conducted a systematic review of such studies published between 1966 and 1998. Studies were assessed against BMJ economic evaluations guidelines for each stage (guideline development, implementation and treatment). Of 235 studies identified, 63 reported some information on cost. Only 3 studies provided evidence that their guideline was effective and efficient, 38 reported treatment costs only, 12 implementation and treatment costs, 11 implementation costs alone, and 2 guideline development, implementation and treatment costs. No study gave reasonably complete information on costs. Thus, very few satisfactory economic evaluations of guideline implementation strategies have been performed. Current evaluations have numerous methodological defects and rarely consider all relevant costs and benefits. Future evaluations should focus on evaluating the implementation of evidence-based guidelines.