Systematic reviews apply strategies that limit bias to the assembly, appraisal, and synthesis of relevant studies on a specific topic.1,2 We followed published guidelines3,4 to search the National Library of Medicine's Medline and the Cochrane library databases (January 1, 2000 to January 17, 2010, date of last search) for prospective, randomized, controlled trials (RCTs) of IV acetaminophen vs. either an active comparator (except for propacetamol) or placebo on adult patients undergoing surgery and receiving general anesthesia, regional anesthesia, sedation, or local anesthesia. We limited our review to English language articles. Data from posters/abstracts, letters, retrospective trials, case reports, and unpublished data were not considered. No minimum sample sizes were required for inclusion of studies.