Abstract： Background Erectile dysfunction (ED) is a common impairment among older men, and the prevalence rates increase sharply after age of 60 years. Most studies have focused on the prevalence rate or dangerouse factors. The aim of this study was to investigate the basic epidemiologic data about ED patients with different ED courses. The purpose of this researth was to understand the therapeutic effect of phosphodiesterase type 5 inhibitor (PDE5-1) and see how and why the ED course impact the progress of ED and the therapeutic effect of PDE5-1 treatment.Methods From June 2008 to June 2009, 4252 questionnaires (Quality of Erection Questionnaire, QEQ) were gathered from 46 centers by urology or andrology doctors all around China. Patients with ED (age ＞ 20 years) filled in first half of the questionnaires when they came for the first time, and then completed the second half 4 weeks after PDE5-1 therapy.Results ED courses of most patients were less than 5 years (＜5 years, 74.0%; 5-10 years 20.8%; ＞10 years, 5.2%). As ED course increasing, the incidence of the risk factors of ED, such as smoking, drinking, hypertension, diabetes, heart disease and hyperlipidemia also increase (P ≤0.01). PDE5-1 was effective in improving the quality of sexual activities (P ≤0.01). Administration of PDE5-1 improves satisfaction, enjoyment and frequency of sexual activities. The longer the ED course, the worse the therapeutic effect (＜5 years, 96.1%; 5-10 years, 94.9%; ＞10 years, 89.0%) (P＜0.01).Conclusions The ED course greatly affected the therapeutic effect of PDE5-1, the patients with ED should consult doctor at early stage of the disease. Admistration of PDE5-1 effectively improves the penile erection and the quality of sexual life of the patients hence should be considered as first-line medicine in the treatment of ED.