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—To identify the extent to which meta-analyses currently include unpublished data and whether editors, meta-analysts, and methodologists believe unpublished material should be included.

—This article describes two related studies: a literature review and a cross-sectional survey.

—For the literature review, we identified all articles indexed by the key word meta-analysis from January 1989 to February 1991 and determined whether unpublished material had been searched for, obtained, and included in the meta-analyses. For the cross-sectional survey, we surveyed authors of these meta-analyses, authors of articles addressing methodological issues in metaanalysis published during the same period, and editors of journals in which both types of articles were published.

—We asked the respondents about their attitudes concerning inclusion of unpublished data and …