We surveyed 1005 postdoctoral fellows by questionnaire about ethical matters related to biomedical research and publishing; 33% responded. About 18% of respondents said they had taken a course in research ethics, and about 31% said they had had a course that devoted some time to research ethics. A substantial majority stated willingness to grant other investigators, except competitors, access to their data before publication and to share research materials. Respondents’ opinions about contributions justifying authorship of research papers were mainly consistent (...) but at variance with those of many biomedical journal editors. More than half said they had observed what they considered unethical research practices. To increase the chances of getting a grant funded, 27% said they were willing to select or omit data to improve their results; to make publication of their work more likely or to benefit their career, 15% would select or omit data and 32% would list an undeserving author. Of respondents who thought they had been unfairly denied authorship on a paper, or been listed with or asked to list an undeserving author, 75% said they would be willing to list an undeserving author (P<0.001). Having taken a course dealing with research ethics had no effect on stated willingness to select or omit data or to fabricate data in the future, but was positively associated with willingness to grant undeserved authorship (P<0.04). Although these results do not controvert research demonstrating the effectiveness of ethics courses during professional education, they indicate that the research environment is a powerful component of a trainee’s experience and ethical development. (shrink)