An increasing number of science courses now include consideration of the ethical implications of science. However, there is little agreement about how ethical reasoning in science should be assessed. This article highlights the conclusions of a seminar on the assessment of ethics in science that was organized by the Nuffield Foundation Curriculum Programme and the Nuffield Council on Bioethics. It includes the eight recommendations of the resulting report. These relate to the differences between ethics and science, the demands placed on science teachers, the importance of student progression, the design of examination questions, the design of mark schemes, and teacher development. (Contains 1 figure, 3 boxes, and 4 online resources.)