The article is a contribution in the debate about knowledge in science and knowledge in practice. The first part is a historical retrospect of ideas about ethical responsibility and ethical values for nurses as they have been represented in textbooks for nurses. The second part illuminates how knowledge in science and knowledge in practice appear in the educational thinking today. The third part focus on how ethical knowledge can be developed according to the theory about ethical decision making in practice. Ethical knowledge is about ethical sensitivity and moral reasoning ability. Ethical theory can help in developing ethical knowledge but it is not a guarantee for ethical and moral responsibility in practicing nursing.