Introduction: Although there are many methods in the treatment of erectile dysfunction, no one is successful and sufficient in all the patients. Sildenafil treatment has been found the most successful method among ED treatments. In spite of high efficacy of sildenafil, some patients still stop sildenafil treatment due to various reasons. The aim of the present study is to evaluate the causes of sildenafil citrate treatment discontinuation in the patients with erectile dysfunction. Materials and methods: A total of 217 patients who admitted to our outpatient clinic due to erectile dysfunction were included in the study. They were evaluated with a detailed medical and sexual history and physical examination. Erectile function was assessed with IIEF scores before and after the treatment. The patients' ages ranged from 22 to 74 years (52.3±11.7). They suffered from erectile dysfunction for 34.3±31.3 months (2-240 months). Sildenafil citrate 50 mg was given for a month. At the end of this period, patients were re-evaluated and questioned about the efficacy of sildenafil citrate, its' side effects and whether they wanted to continue the treatment or not. Later, sildenafil 100 mg was recommended to patients desiring to use higher dose of it, and they were questioned 4 week later. Finally, the efficacy and side effects of sildenafil was evaluated, and the causes of dropout were obtained from the patients who discontinued sildenafil treatment. Results: At the 4th week control, sufficient erection was observed in 163 patients (75.1%), no erection was encountered in 54 patients (24.9%). Out of 163 patients, 131 (80.4%) who had sufficient erection with sildenafil left the treatment. The causes of discontinuation in these patients were the high price of the drug in 86 patients (%65.6), improvement of erection problem in 26 (%19.8), fear of asparagus news appearing in the media in 12 patients (%9.2), and side effects of sildenafil in 7 patients (%5.3). Of sildenafil failed patients (n: 54), 12 (22.2%) accepted to try sildenafil 100 mg, 42 (77.8%) did not accept to try sildenafil 100 mg. The reasons not, to try sildenafil 100 mg for these patients were high prize in 20 patients (47.6%), consideration of penile prosthesis in 2 patients (3.2%), side effects of sildenafil 50 mg in 13 patients (30.9%), nothing for 7 patients (16.7%). At the end of the treatment period, only 35 (16.1%) patients continued to use sildenafil 50 or 100 mg, 182 patients (83.9%) left the treatment due to different causes. These causes were high prize in 108 patients (59.3%), improvement of erection quality in 26 patients (14.3%), side effects in 20 patients (10.9%), asparagus news in 12 patients (6.6%), inefficacy in 7 patients (3.8%), choosing other treatment alternatives in 2 patients (1.1%). The other 7 (3.8%) did not describe any cause. Side effects were headache in 15 patients (6.9%), sweating in 12 patients (5.5%), visual problems in 6 patients (2.8%) and chest pain in 4 patients (1.8%). Conclusion: Although Sildenafil treatment is found very effective with acceptable side effects in the treatment of ED regardless to the etiology, discontinuation of the drug is very high. In this study, 80.4% of the patients in whom sildenafil treatment was successful left the treatment. The most important factor of this low ratio is the difficulty of buying the drug due to economic problems.