Study to Evaluate Viagra's Ability to Provide a Better Sexual Experience Through Quality Erections and Satisfaction

Inclusion Criteria: * Male subjects aged 18-65. * Documented clinical diagnosis of erectile dysfunction confirmed by an IIEF-EF Domain score of less than or equal to 25. (If the subject scores greater than 25 on the IIEF-EF Domain, screening procedures should be terminated.) Exclusion Criteria: * Subjects who have been treated with more than 6 doses of sildenafil citrate or any other phosphodiesterase type 5 (PDE-5) inhibitor such as vardenafil or tadalafil for erectile dysfunction \[Note: subjects should not have taken any PDE-5 inhibitors within 4 weeks prior to the date of screening\].