This study assessed the hypothesis that the formal teaching of medical ethics promotes a significant increase in the growth and development of moral reasoning in medical students. Results indicated a statistically significant increase (P less than or equal to 0.0005) in the level of moral reasoning of students exposed to a medical ethics course compared to the control group that was not exposed to the medical ethics course. When the posttest scores were adjusted by subtracting the pretest scores, the differences were even more significant (P less than or equal to 0.0002). This study confirmed similar findings of another study using a different instrument of assessment. Brief discussion is given of the fundamental premise that the appropriate function of teaching medical ethics in our modern pluralistic society is to improve students' moral reasoning about value issues regardless of what their particular set of moral values happens to be.