A survey was used from 1983 through 1990 in a required first-year course, Ethics and Medical Care, at The Johns Hopkins University School of Medicine, to explore where students drew the line about moral issues. Starting in 1988, a similar questionnaire was administered to each class of fourth-year medical students. This report summarizes the students' attitudes--reported anonymously in both surveys--regarding circumstances under which they would perform or refer for an abortion. Attitudes towards abortion changed little in four years. Comfort levels with patient referral were greatest when the life of the mother was threatened and in the case of rape. Students' attitudes correlated most strongly with personal beliefs about when a fetus was considered a human life and less so with students' genders. The first-year survey results were shared with the students in the course's annual sessions on abortion in order to aid them in understanding the assumptions underlying ethical dilemmas surrounding abortion and to make visible the class's moral pluralism on the subject. The survey also helped them determine their tolerance, if any, for patients' views or actions that conflicted with their personal moral stances.