Overviews of reviews incompletely report methods for handling overlapping, discordant and problematic data. Journal of Clinical Epidemiology, Volume 0, Issue 0 Found at: https://www.jclinepi.com/article/S0895-4356(18)31062-X/fulltext - This version is the abstract only To request full access of the article, please email the authors at carole.lunny (at) ti.ubc.ca Abstract Background: Overviews of systematic reviews should be fully reported to allow readers to assess the adequacy of the methods and validity of the findings. Previous studies have reported a need for increased rigour and more complete reporting of methods in overviews. Objective: To assess the completeness of reporting of methods in overviews. Study Design and Setting: A published framework of methods for conducting an overview was used as the basis for assessing the adequacy of the reporting of the methods in a random sample of 50 overviews. Descriptive summary statistics were presented using frequencies and percentages for categorical data and medians and interquartile ranges (IQR) for continuous data. Results: We screened 848 randomly selected abstracts to obtain the required 50 overviews. A median of 13 (IQR 7-32) systematic reviews (SRs) were included in the overviews. Overview characteristics were: 22% reported working from a protocol; 36% reported using reporting standards (e.g. PRISMA, QUORUM); and 34% reported using methodological guidance (e.g. Cochrane Handbook). Methods common to both overviews and SRs of primary studies were reported in majority of overviews (e.g. 56% framed the overview question by PICO elements, 44% reported methods for specifying eligibility criteria, and 76% reported assessing risk of bias of reviews). The exceptions were reporting methods for summarising the evidence (20%) and statistical synthesis (26%), which were not commonly reported. Methods pertaining to more unique aspects of overviews were underreported across the majority of items. For example, methods for dealing with overlap in the primary studies included in SRs (30%), methods to handle problematic (i.e. discrepant or missing) data across reviews during data extraction (14%), and methods to deal with discordance in the results, or their interpretation, across reviews (20%). Conclusions: The most completely reported methods in overviews were those common to SRs of primary studies while the more unique methods were underreported. Our findings provide a benchmark of the completeness of reporting of overview methods and may inform the development of guidance for preparing protocols of overviews.