During the past few decades, engineering ethics has been oriented towards protecting the public from professional misconduct by engineers and from the harmful effects of technology. This "preventive ethics" project has been accomplished primarily by means of the promulgation of negative rules. However, some aspects of engineering professionalism, such as (1) sensitivity to risk (2) awareness of the social context of technology, (3) respect for nature, and (4) commitment to the public good, cannot be adequately accounted for in terms of rules, certainly not negative rules. Virtue ethics is a more appropriate vehicle for expressing these aspects of engineering professionalism. Some of the unique features of virtue ethics are the greater place it gives for discretion and judgment and also for inner motivation and commitment. Four of the many professional virtues that are important for engineers correspond to the four aspects of engineering professionalism listed above. Finally, the importance of the humanities and social sciences in promoting these virtues suggests that these disciplines are crucial in the professional education of engineers.