Genetic variation is essentially randomly inherited from parents to offspring at conception, and consequently, many factors that confound the association between the exposure and outcome cannot affect the genetic variants. 8 MR studies use genetic variants robustly related to modifiable exposures to understand the influence of the exposure on various health, social, and economic outcomes. These genetic variations can be used as instrumental variables to analyse the effect of modifiable exposures on diseases through a study method termed mendelian randomisation (MR). Over the past decade, advances in genetic technologies have enabled the identification of thousands of reproducible associations between genetic variation and relevant exposures, traits, and health outcomes. 6 For example, instrumental variable methods rely on an external factor that determines the exposure of interest but is not associated with the outcome other than through its effect on the exposure. 4 5 Several approaches have been developed with the aim of mitigating such biases. In turn, ill health could be related to a reduction or cessation of alcohol consumption, introducing potential bias due to reverse causality, when interest is in studying the effect of alcohol consumption on subsequent health. For example, alcohol consumption might be related to many potential confounding factors, including smoking, an unhealthy diet, and limited exercise. However, such associations reported in epidemiological studies are often not reliable estimates of causal effects, and can be produced by confounding (that is, by another factor that affects both the outcome and exposure) 1 2 3 or by other forms of bias. Observational epidemiology often examines the associations between exposures and health outcomes. Examples of transparent reporting are used for each item to illustrate best practices. This article explains the 20 items of the STROBE-MR checklist, along with their meaning and rationale, using terms defined in a glossary. Adopting STROBE-MR should help readers, reviewers, and journal editors evaluate the quality of published MR studies. STROBE-MR (strengthening the reporting of observational studies in epidemiology using mendelian randomisation) assists authors in reporting their MR research clearly and transparently. Reporting guidelines help authors effectively communicate all critical information about what was done and what was found. Mendelian randomisation (MR) studies allow a better understanding of the causal effects of modifiable exposures on health outcomes, but the published evidence is often hampered by inadequate reporting.