Over the last 25 years, a small but growing body of research on research behavior has slowly provided a more complete and critical understanding of research practices, particularly in the biomedical and behavioral sciences. The results of this research suggest that some earlier assumptions about irresponsible conduct are not reliable, leading to the conclusion that there is a need to change the way we think about and regulate research behavior. This paper begins with suggestions for more precise definitions of the terms "responsible conduct of research," "research ethics," and "research integrity." It then summarizes the findings presented in some of the more important studies of research behavior, looking first at levels of occurrence and then impact. Based on this summary, the paper concludes with general observations about priorities and recommendations for steps to improve the effectiveness of efforts to respond to misconduct and foster higher standards for integrity in research.