ZusammenfassungGaining informed consent from people being researched is central to ethical research practice. There are, however, several factors that make the issue of informed consent problematic, especially in research involving members of groups that are commonly characterised as ‘vulnerable’ such as children and people with learning disabilities. This paper reports on a project funded by the UK Economic and Social Research Council (ESRC) which was concerned to identify and disseminate best practice in relation to informed consent in research with six such groups. The context for the study is the increased attention that is being paid to the issue of informed consent in research, not least because of the broad changes taking place in research governance and regulation in the UK. The project involved the analysis of researchers’ views and experiences of informed consent. The paper focuses on two particular difficulties inherent in the processes of gaining and maintaining informed consent. The first of these is that there is no consensus amongst researchers concerning what comprises ‘informed consent’. The second is that there is no consensus about whether the same sets of principles and procedures are equally applicable to research among different groups and to research conducted within different methodological frameworks. In exploring both these difficulties we draw on our findings to highlight the nature of these issues and some of our participants’ responses to them. These issues have relevance to wider debates about the role of guidelines and regulation for ethical practice. We found that study participants were generally less in favour of guidelines that regulate the way research is conducted and more in favour of guidelines that help researchers to strike balances between the conflicting pressures that inevitably occur in research.