ABSTRACT In Mexico informed consent is a legal requirement that ensures that patients who are invited to participate in clinical trials are provided with all the information needed to decide whether to participate, or not, in a research protocol. To improve our understanding of the problems physicians in developing countries encounter, when obtaining informed consent (IC), we examined their opinion on the importance of IC in clinical research, the quantity and quality of the information provided to the participant, and the (...) conditions in which the IC is obtained. Investigators considered that IC was useful to the patients, providing information that helped the patient to make a decision about his/her participation. Nevertheless, they felt that for some aspects of the research, like drug development in general, the use of placebos, and the randomization process, many of the patients were not capable of fully understanding the information provided, referring to the complexity of the information and illiteracy as the main reasons. Many investigators were not acquainted with some of the guidelines established in the Mexican General Law of Health,1 36% of them admitting to not having completed their IC letters. Most investigators gave only minutes to the patient to make a decision and 20% of ICs were obtained while the patient was hospitalized. Except for one investigator, all of them considered that specific training in medical ethics would be useful for the daily clinical work. (shrink)