RESUMO
Esophageal cancer is highly prevalent among the Turkman people in Northeastern Iran. In order to evaluate its etiology, there is an on-going prospective cohort study in this area involving approximately 50000 subjects over the age of 40 years. The majority of these subjects are illiterate, thus obtaining informed consent is very important and difficult. Initially, we explained the aim and study method to religious leaders and health-sanitary officials. One week prior to obtaining informed consent, potential participants were given adequate information about the research process by trained health personnel at their own home. Thus, participants had sufficient time to consider the research and consult with local health personnel, religious authorities, family, neighbors, friends and those who previously participated in the study. Potential participants could observe the research process directly and then be included in the study if they agreed. A total of 50045 individuals agreed to participate in the study, of which 70% were illiterate. There were no refusals due to the medical ethical aspects of this study. The method of awareness in this study can be a useful pattern for research on elderly and illiterate individuals who are participants in research studies in Iran and other countries