The purpose of this review was to provide an overview of the empirical literature on nurses’ codes of ethics in practice and education covering the time from 1980 to August 2007. The focus was on methodological issues, main domains of interest and findings of the studies. The aim of the review was to identify knowledge gaps and to provide recommendations for further research. Research on the codes of ethics in nursing is scarce. The main domains of interest were education, nurses’ knowledge and use of the codes, the content and functions of the codes, and moral behaviour and values related to the codes. Education of the codes was important, and it had a positive impact on students’ moral behaviour measured by an instrument based on the codes. Nurses’ knowledge and use of the codes was deficient. Nurses’ practice was guided by environmental contexts and personal experiences rather than the codes. However, nurses’ values espoused those of the codes. The nurse–patient relationship was the best known aspect of the codes. Methodological diversity, a small number of studies focusing on several domains of interest warrants care in the interpretation of the findings. Further research should focus particularly on the education of the codes, covering the realization of the teaching process, evaluation of outcomes and organization of education. Cooperation between theoretical education and clinical practice should be explored. Research of the meaning of the codes and their functions for nurses, nurses’ moral behaviour and professional values is needed. Research should cover all levels and areas of nursing and reach beyond the nurse–patient relationship to relationships with colleagues, other health professions, organizations and the society. The use of more varied methodological approaches is suggested.