Scholars have proposed a number of courses and programs intended to improve the ethical behavior of scientists in an attempt to maintain the integrity of the scientific enterprise. In the present study, we conducted a quantitative meta-analysis based on 26 previous ethics program evaluation efforts, and the results showed that the overall effectiveness of ethics instruction was modest. The effects of ethics instruction, however, were related to a number of instructional program factors, such as course content and delivery methods, in addition to factors of the evaluation study itself, such as the field of investigator and criterion measure utilized. An examination of the characteristics contributing to the relative effectiveness of instructional programs revealed that more successful programs were conducted as seminars separate from the standard curricula rather than being embedded in existing courses. Furthermore, more successful programs were case based and interactive, and they allowed participants to learn and practice the application of real-world ethical decision-making skills. The implications of these findings for future course development and evaluation are discussed.