Scientific and technological improvements are accomplished only because of much research. The increase in the number of research studies causes a rise in ethical problems. Nursing research is no exception to this. The aim of this study is to identify and analyse ethical problems in nursing studies. This research is descriptive and partly analytical. It is retrospective in the sense that 169 Master of Science and 66 doctoral theses written between 1972 and 1998 in the Department of Nursing, Institute of Health Sciences, Hacettepe University, Ankara, Turkey, were examined. The following ethical rules were used as criteria: that no harm should be caused to the subject; the subject was informed about the research topic; permission was obtained from the subject; and the privacy of the subject was maintained. The evaluation was carried out by distributing the theses among background variables and by employing nonparametric tests. The research associated with the theses was not harmful to the participants in 93.2%, while 6.8% were considered to have caused harm. In 72.7% of the theses the subjects were not informed of the research; in 73.6%, the researchers did not obtain permission from the subjects; and in 8.5% their privacy was not kept. An ethical score was assigned to each thesis, which varyed between 0 and 15. The mean score was 5.02.