The main purpose of the present paper is to study the degree of observation of ethical standards in the PhD theses at the Faculty of Humanities of Ferdowsi University, Mashad. Content analysis has been employed for the purpose of this study. All PhD theses defended in a period of five years between 2007 and 2012 have been analyzed  by using the researcher-made list. The following elements have been  used in the list:  observation of the rights of participants, observation of ethical principles in giving references and sources, observation of ethical principles in preparation of research report and having ethical codes.  The findings of the research indicate that some ethical standards have been observed in major chunk of the PhD theses, while other standards of research ethics have either been neglected or have not been precisely reported. For example, the findings indicate that in most of the theses (75 percent) the following elements have been observed: anonymity of participants, secrecy, clarity of the method of data collection, report on validity of research tools , clarity of method of data analysis, congruity of the method of data analysis with the method of conducting research, and having ethical code. Also in 50 percent of the theses reference standards have been observed, while in 5 percent of the theses the following elements have been taken into consideration: getting conscious consent, giving information about the objectives and nature of the research to the participants, introduction of the researcher to the respondents, health and convenience of the participants, seeking a remedy for negative consequences of research and preparation of a stress-free environment.