Background Informed consent is a critical component of clinical research. Different methods of presenting information to potential participants of clinical trials may improve the informed consent process. Audio-visual interventions (presented, for example, on the Internet or on DVD) are one such method.We updated a 2008 review of the effects of these interventions for informed consent for trial participation. Objectives To assess the effects of audio-visual information interventions regarding informed consent compared with standard information or placebo audio-visual interventions regarding informed consent for potential clinical trial participants, in terms of their understanding, satisfaction, willingness to participate, and anxiety or other psychological distress. Search methods We searched: the Cochrane Central Register of Controlled Trials (CENTRAL), The Cochrane Library, issue 6, 2012; MEDLINE (OvidSP) (1946 to 13 June 2012); EMBASE (OvidSP) (1947 to 12 June 2012); PsycINFO (OvidSP) (1806 to June week 1 2012); CINAHL (EbscoHOST) (1981 to 27 June 2012); Current Contents (OvidSP) (1993Week 27 to 2012Week 26); and ERIC (Proquest) (searched 27 June 2012). We also searched reference lists of included studies and relevant review articles, and contacted study authors and experts. There were no language restrictions. Selection criteria We included randomised and quasi-randomised controlled trials comparing audio-visual information alone, or in conjunction with standard forms of information provision (such as written or verbal information), with standard forms of information provision or placebo audio-visual information, in the informed consent process for clinical trials. Trials involved individuals or their guardians asked to consider participating in a real or hypothetical clinical study. (In the earlier version of this review we only included studies evaluating informed consent interventions for real studies). Data collection and analysis Two authors independently assessed studies for inclusion and extracted data. We synthesised the findings using meta-analysis, where possible, and narrative synthesis of results. We assessed the risk of bias of individual studies and considered the impact of the quality of the overall evidence on the strength of the results. Main results We included 16 studies involving data from 1884 participants. Nine studies included participants considering real clinical trials, and eight included participants considering hypothetical clinical trials, with one including both. All studies were conducted in high-income countries. There is stillmuch uncertainty about the effect of audio-visual informed consent interventions on a range of patient outcomes.However, when considered across comparisons, we found low to very low quality evidence that such interventions may slightly improve knowledge or understanding of the parent trial, but may make little or no difference to rate of participation or willingness to participate. Audiovisual presentation of informed consent may improve participant satisfaction with the consent information provided. However its effect on satisfaction with other aspects of the process is not clear. There is insufficient evidence to draw conclusions about anxiety arising from audio-visual informed consent. We found conflicting, very low quality evidence about whether audio-visual interventions took more or less time to administer. No study measured researcher satisfaction with the informed consent process, nor ease of use. The evidence from real clinical trials was rated as low quality for most outcomes, and for hypothetical studies, very low. We note, however, that this was in large part due to poor study reporting, the hypothetical nature of some studies and low participant numbers, rather than inconsistent results between studies or confirmed poor trial quality. We do not believe that any studies were funded by organisations with a vested interest in the results.