The effectiveness and tolerability of 12 weeks of open-label treatment with sildenafil citrate for erectile dysfunction (ED) associated with a diagnosis of diabetes mellitus and/or hypertension were assessed in clinical practice in three Middle Eastern countries. The dose was initially 50 mg and was adjusted by the physician as needed (permissible dose range 25 - 100 mg). Total mean ± SD score on the five-item version of the International Index of Erectile Function (severe ED, score 0 - 7; no ED, score 22 - 25) was 13.6 ± 5.7 at baseline (4556 patients) and increased significantly to 21.7 ± 4.1 at week 12. Global effectiveness was rated as good or very good by 91.4% of patients, 93.9% rating their sexual activity as spontaneous and 91.4% as natural. Discontinuation of sildenafil due to adverse events was infrequent (0.5%). Tolerability was rated as good or very good by 95.7% of patients. It is concluded that sildenafil was a well-tolerated and highly effective treatment of ED in outpatients with diabetes and/or hypertension from the three Middle Eastern countries studied.