This report updates a 2000 Health Technology Assessment (HTA) review on publication and related biases. It examines empirical studies on publication and related biases since 1998, assesses methods to address these biases, and evaluates measures to prevent, reduce, and detect dissemination bias in a sample of published systematic reviews. The review finds that studies with significant or positive results are more likely to be published than those with non-significant or negative results, confirming previous findings. There is convincing evidence of outcome reporting bias, which affects the pooled summary in systematic reviews. Published studies tend to report greater treatment effects than those from grey literature. Excluding non-English language studies increases bias in some areas of research. Publication bias can be prevented before a literature review (e.g., by prospective registration of trials), detected during a literature review (e.g., by locating unpublished studies, funnel plots), or minimized after a literature review (e.g., by confirmatory large-scale trials). The interpretation of funnel plots and related statistical tests is often too simplistic and misleading. More sophisticated methods are needed. Recent reviews are more likely to include non-English language studies and grey literature, and to test for publication bias. The report concludes that dissemination of research findings is likely to be biased, but the actual impact depends on specific circumstances. Prospective registration of clinical trials and endorsement of reporting guidelines may reduce dissemination bias. In systematic reviews, measures can be taken to minimize the impact of dissemination bias by systematically searching for and including relevant studies. Statistical methods can be useful for sensitivity analyses. Further research is needed to develop methods for qualitatively assessing the risk of publication bias and to evaluate the effect of prospective registration, open access policy, and improved publication guidelines. The report also discusses the sources of publication bias, including investigators, editors, research sponsors, and variations in study results. Methods to prevent, reduce, or detect publication bias include prospective registration of trials, open access policy, and confirmatory large-scale trials. The report emphasizes the importance of making all study results accessible and the need for further research to address publication bias in clinical trials and health policy decision-making.This report updates a 2000 Health Technology Assessment (HTA) review on publication and related biases. It examines empirical studies on publication and related biases since 1998, assesses methods to address these biases, and evaluates measures to prevent, reduce, and detect dissemination bias in a sample of published systematic reviews. The review finds that studies with significant or positive results are more likely to be published than those with non-significant or negative results, confirming previous findings. There is convincing evidence of outcome reporting bias, which affects the pooled summary in systematic reviews. Published studies tend to report greater treatment effects than those from grey literature. Excluding non-English language studies increases bias in some areas of research. Publication bias can be prevented before a literature review (e.g., by prospective registration of trials), detected during a literature review (e.g., by locating unpublished studies, funnel plots), or minimized after a literature review (e.g., by confirmatory large-scale trials). The interpretation of funnel plots and related statistical tests is often too simplistic and misleading. More sophisticated methods are needed. Recent reviews are more likely to include non-English language studies and grey literature, and to test for publication bias. The report concludes that dissemination of research findings is likely to be biased, but the actual impact depends on specific circumstances. Prospective registration of clinical trials and endorsement of reporting guidelines may reduce dissemination bias. In systematic reviews, measures can be taken to minimize the impact of dissemination bias by systematically searching for and including relevant studies. Statistical methods can be useful for sensitivity analyses. Further research is needed to develop methods for qualitatively assessing the risk of publication bias and to evaluate the effect of prospective registration, open access policy, and improved publication guidelines. The report also discusses the sources of publication bias, including investigators, editors, research sponsors, and variations in study results. Methods to prevent, reduce, or detect publication bias include prospective registration of trials, open access policy, and confirmatory large-scale trials. The report emphasizes the importance of making all study results accessible and the need for further research to address publication bias in clinical trials and health policy decision-making.