The aim of this study was to analyse the impact of assistance on the comprehensibility and reliability of the Turkish version of International Index of Erectile Function (IIEF). In this study, 458 patients were asked to complete the IIEF questionnaire by themselves during their first visit and then once again during their second visit with the assistance of a physician. The impact of physician assistance was evaluated by comparing the first and second questionnaires. The data were analysed using statistical package software (spss). A t test, Cronbach's alpha analysis, test–retest correlation (Pearson) and comparison of two rates between two independent groups test were used to analyse the impact of physician assistance. A P value <0.05 was considered to be significant. The proportions of the patients who completed the questionnaires were 70.9% and 100% at the first and second visit respectively. Physician assistance significantly increased the number of patients who completed the questionnaire among patients ≥60 years old (P = 0.0009) and in patients with low levels of education (P = 0.0001). The Cronbach's alpha coefficients were 0.782 and 0.917 for the first and second questionnaires respectively. A high degree of internal consistency was observed for the ‘physician-assisted’ questionnaire (P < 0.001), and relatively less internal consistency was found for the ‘self-administered’ questionnaire (P < 0.05) A relatively weaker correlation was found between the first and second questionnaires in primary school graduates (r = 0.391, P < 0.05) and in patients ≥60 years old (r = 0.433, P < 0.05). There was a significant difference between the ‘self-administered’ and ‘physician-assisted’ IIEF scores in patients ≥60 years old (P < 0.0001) and primary school graduates (P < 0.0001). Physician assistance increased the comprehensibility and reliability of the IIEF questionnaire, especially in elderly patients and in patients with low education levels.