OBJECTIVES: The emergence of evidence-based medicine (EBM) in the past decade has raised the level of the scientific data required during the drug appraisal process. It is no longer sufficient to prove that a new treatment is better than placebo in one clinical trial; healthcare decision makers additionally require information on how it performs in multiple trials, including against other treatments in the disease area. Systematic reviews, meta-analyses, comparative effectiveness studies and head-to-head trials are becoming essential in the appraisal process as decision makers demand higher levels of evidence from manufacturers. This analysis reviewed PubMed articles for trends in the numbers of such studies from 2001-2010. METHODS: The titles of PubMed articles were searched for “systematic review”, “meta-analysis”, “comparative effectiveness” and “head-to-head” along with the year of publication. RESULTS: The mean annual change in the number of articles indexed by PubMed over the period was 6.0%, which represents the background increase in the body of scientific evidence. In contrast, the mean annual change for systematic reviews was 27.4% (from 388 in 2001, to 3406 in 2010), 23.2% for meta-analyses (462 to 2,996), 80.5% for comparative effectiveness studies (5 to 247) and 23.1% for head-to-head trials (11 to 53). These increases are all substantially higher than the background increase in PubMed articles. The increase in comparative effectiveness studies in particular illustrates the strength of interest in this area of research. CONCLUSIONS: EBM is now accepted globally as the preferred method of appraising new treatments; as the pharmaceutical industry adapts to this landscape, the number of studies examining the evidence base has increased considerably in the past decade. The next movement in the industry has already arrived, that of direct comparative effectiveness, and whilst the number of head to head studies has already increased we can expect to see further increases over the next decade.