The objective of this study was to ascertain the views and attitudes of medical investigators on medical ethics, and ethics and fraud in medical research. We sent postal questionnaires to all principal investigators whose study protocols had been assessed by their regional medical ethics committee for biomedical research (mid-Norway) in the years 1986-92 (n = 159). The response rate was 70% (n = 119). Some 80% agreed that ethical considerations had influenced their research and 12% that they would have had ethical scruples today about some of their previous projects. One in ten agreed that they might have achieved better results if they could have paid less attention to ethics. About 70% of the respondents found that the committee's comments were useful and relevant, but most agreed only in part. Around 85% agreed fully or in part that scientific quality is an important ethical element of any project and that researchers put more effort into their study protocol when they knew it would be evaluated by an ethics committee. One in six (18%) respondents agreed fully or in part that they had been exposed to scientific misconduct. Also, 27% knew about one or more cases of fraud or misconduct while 42% stated that this knowledge was not public. We concluded that ethics in medicine and medical research have an important and increasing role among investigators with little or no theoretical background and training in ethics. Scientific fraud and misconduct in medicine is a growing concern among researchers, who welcome a professional body that can manage allegations and cases of fraud.