To evaluate the efficacy of Viagra dose titration to 100mg versus 50mg in men with erectile dysfunction, based on responses to the IIEF questionnaire as measured at the beginning and at the end of double blind treatment, comparing the group titrated to 100mg vs. the group maintained on 50mg.

Inclusion Criteria:

• Documented clinical diagnosis of ED by using IIEF-EF domain with score of ≤ 25.
• Subjects must be in a stable relationship with the same partner for at least 6 months and willing to attempt sexual intercourse.

Exclusion Criteria:

• Subjects in whom sexual activity is inadvisable in the opinion of the investigator such as significant cardiovascular disease in the last 6 months; including cardiac failure, myocardial infarction, unstable angina, stroke or transient ischemic attack (TIA), symptomatic or clinically significant cardiac arrhythmias including atrial fibrillation.
• Subjects who are currently taking or are likely to be treated with nitrates or nitric oxide donors in any form (oral, sublingual, buccal, transdermal, inhalational or as aerosols) on either regular or intermittent basis.