In theory, HREC members should use the ethical guidelines in the National Statement on the Ethical Conduct of Research Involving Humans as the basis for their decisions, and researchers should design their research in accordance with these guidelines. However, very little is known about what researchers and HREC members actually do in practice. In this paper, we report some of the key findings of the study "Human Research Ethics in Practice", a qualitative interview-based study of health researchers and HREC members in Victoria. The findings shed light on how researchers and HREC members conceptualise ethics, how they use the National Statement, and what deliberative strategies they employ to assess the ethical appropriateness of research studies. The findings also reveal differences and similarities between health researchers' and HREC members' perceptions of the roles of HRECs, and point to some sources of misunderstanding and tension. We examine the implications of some of these findings for the ways in which HRECs carry out their task, and research institutions support and promote ethical conduct in research amongst their staff and students. The focus of this study is on health research, but we suggest that the findings are highly relevant to all other research areas where human participants are involved.