The objective of our study is to analyze the impact of patient age, education level, and household income on the understanding of the International Index of Erectile Function (IIEF) and to determine the patient characteristics that make this questionnaire less reliable. All men older than 18 years presenting to our clinic were asked to complete the Turkish translation of IIEF upon arrival. Self-reported information related to age, education level, and household income of the patients was also recorded from the questionnaire. The patients were requested to complete the questionnaires once again during their second visit, which was not earlier than 5 hours and no later than 5 days. The patients were requested to complete the questionnaire by themselves; however, those who were unable to do so themselves were allowed to receive the assistance of their companions. The answers of the questions that were replied to properly were defined as "appropriate," and the unanswered questions or those replied to with more than one answer were defined as "inappropriate." A total of 430 patients were included in this study. Only 289 patients (67.2%) were able to respond to all of the questions properly at first visit. The percentage of improper completion increased as age increased, whereas it decreased parallel to the increase in educational level and household income (respectively, P = .027, P < .001, P = .008). Of 430 patients, 68.4% did not need any help from their companions, and the remaining 31.6% needed some assistance during the completion of the questionnaire. A total of 131 patients who completed the questionnaire at their initial admittance to our clinic came for their second visit. Only 61.8% of the patients were capable of completion both at first and second visits. There was a low degree of consistency among the first and second administrations of IIEF (k = 0.369, P < .001). Turkish translation of the IIEF needs further validations for the self-administered mode in order to improve its comprehension as well as its reliability, validity, and specificity, especially in older patients with lower educational levels and household income status, among whom the prevalence and the severity of erectile dysfunction is higher.