OBJECTIVES: To determine the proportion of published cost-minimization analyses (CMAs) that provided appropriate evidence of equivalence between drug comparators. METHODS: Medline, Embase, and International Pharmaceutical Abstracts (from inception to December 2006) were searched using the words “cost” and “minimization”. Included articles were those that: claimed to be a CMA, compared costs between drugs, reported original research, and were available as full-text (abstracts/reviews/letters were not accepted). Data extraction was performed by two independent reviewers and included: evidence of equivalence, journal type, publication date, and class of drug. To determine adequacy of evidence of equivalence, each article was assessed for source of data as well as strength of effectiveness between comparators, and categorized as: ‘adequate', ‘questionable', and ‘inadequate'. All differences in raters' decisions were resolved through consensus. RESULTS: A total of 67 articles were assessed for evidence of equivalence. Of those, the majority were from the US/Canada, followed by Europe. Only one article was from outside these regions (Australia). CMAs were most published in general medicine journals and in the field of cardiovascular drugs. Of the total accepted studies, 9 (13.4%) were judged ‘adequate', 21 studies (31.3%) were categorized as ‘questionable', and 37 (55.2%) studies had ‘inadequate' evidence of equivalence of comparators. The majority of studies failed to prove their comparators' equivalence because the evidence in the literature supported different outcome results, because some of these studies simply assumed equivalence, or did not provide any evidence at all. No correlation was found between studies that provided ‘adequate' or ‘inadequate' equivalence and year of publication. CONCLUSION: The majority of studies failed to provide adequate evidence of the suitability of CMA as an analytic technique. Guidelines should be developed that explicitly specify criteria for the performance of a CMA in future studies.