RT Journal A1 Cook D, Giacomini M T1 THe trials and tribulations of clinical practice guidelines JF JAMA JO JAMA YR 1999 FD May 26 VO 281 IS 20 SP 1950 OP 1951 DO 10.1001/jama.281.20.1950 UL http://dx.doi.org/10.1001/jama.281.20.1950 AB Reports critiquing the validity of randomized trials,1 meta-analyses,2 diagnostic test studies,3 and economic evaluations4 have challenged researchers to improve the conduct of their studies and have encouraged readers to interpret them carefully. The study by Shaneyfelt and colleagues5 in this issue of THE JOURNAL tackles the clinical practice guideline industry, asking fundamental questions about how well they measure up to contemporary standards. Most guidelines outlined their rationale, specified the benefits and harms of health practices, and cited their evidentiary sources. However, guidelines much less often described how the evidence was found, how its worth was judged, and how diverse sources of evidence were combined to formulate recommendations.