OBJECTIVES: The Guidelines is a guidance document to assist those doing economic evaluations produce standardized and reliable economic information for the users of the information (e.g. decision-makers in Canada's publicly-funded health care system). The main changes in this 3rd edition will be discussed. METHODS: CCOHTA has revised the 1997 edition of the Guidelines to ensure it remains current, taking into account of methodological developments and other significant changes since 1997. Each Guideline section provides guidance on preferred methods and advice in areas of controversy. Key stakeholders, including jurisdictions, industry and methodological experts, were consulted. Judgement was needed to strike the proper balance between theoretically ideal vs pragmatic approaches. RESULTS: Key changes include emphasis on: 1) using cost-effectiveness and cost-utility analyses; 2) presenting the payer perspective; 3) using "usual" and recommended care for the comparator; 4) appropriate analysis of effectiveness parameters; 4) using probabilistic and Bayesian analyses for analyzing uncertainty; 6) using stratified analysis; and 7) identifying distributional effects of the technology. Appendices include: 1) guidance on evaluating non-drug technologies; 2) changes to the standardized reporting format; 3) guidance on modelling; 4) guidance on reviewing economic studies; 5) quality assurance tips for doers; and 6) tips for decision-makers on the use and interpretation of economic evidence. Presenting methods and results in a transparent manner is a key principle of the Guidelines. CONCLUSIONS: The CCOHTA Guidelines for conducting economic evaluations has been updated. The extent to which those doing economic evaluations follow the Guidelines, and the degree to which decision-makers actually use the resulting economic evidence for decision-making, will reflect the value of the new Guidelines.