What moral misgivings may arise in connection with the financing of research? Does the source of the funds for a research project matter? Tobacco exemplifies this problem well. Tobacco smoking is the largest single cause of illness and premature death in the industrialized world, but the tobacco industry is also one of its most profitable commercial undertakings. Decades of increasing scientific evidence for the harmfulness of smoking have increased the moral pressure on manufacturers. Good relations with the scientific community is a desirable way to demonstrate the legitimacy of their operations. Medical researchers should act in accordance with the classical ethical principles of medicine; autonomy, doing good, justice and doing no harm. The activities of the tobacco manufacturing companies are not in accordance with these principles. Every medical researcher or physician who uses funding from the tobacco companies cannot escape the fact of lending his or her name to the manufacture of a lethal product.