BACKGROUND:The PRISMA (Preferred Reporting Items of Systematic reviews and Meta-Analyses) Statement was published to help authors improve how they report systematic reviews. It is unknown how many journals mention PRISMA in their instructions to authors, or whether stronger journal language regarding use of PRISMA improves author compliance. METHODOLOGY/PRINCIPAL FINDINGS:An Internet-based investigation examined the extent to which 146 leading medical journals have incorporated the PRISMA Statement into their instructions to authors. Results were analyzed using descriptive statistics. Also, systematic reviews published in the leading anesthesiology journals and the QUOROM (QUality Of Reporting Of Meta-analyses) Statement were used to explore the hypothesis that indicating compliance with the QUOROM Statement in the manuscript is associated with improved compliance with the reporting guideline. In a sample of 146 journals publishing systematic reviews, the PRISMA Statement was referred to in the instructions to authors for 27% (40/146) of journals; more often in general and internal medicine journals (7/14; 50%) than in specialty medicine journals (33/132; 25%). In the second part of the study, 13 systematic reviews published in the leading anesthesiology journals in 2008 were included for appraisal. Mention of the QUOROM Statement in the manuscript was associated with higher compliance with the QUOROM checklist (P = 0.022). CONCLUSIONS/SIGNIFICANCE:Most of the leading medical journals used ambiguous language regarding what was expected of authors. Further improvement on quality of reporting of systematic reviews may entail journals clearly informing authors of their requirements. Stronger directions, such as requiring an indication of adherence to a research quality of reporting statement in the manuscript, may improve reporting and utility of systematic reviews.