Study to Determine a Preference Between Sildenafil or Tadalafil Treatment for Problems Getting an Erection

Switching From Sildenafil Citrate to Tadalafil in Treatment of Erectile Dysfunction: Assessment of Treatment Preference

To determine if men with problems getting and keeping an erection prefer treatment with tadalafil or sildenafil.

Inclusion Criteria:

• History of erection problems
• Anticipate a monogamous female sexual relationship
• Abstain from other erection treatments throughout the study
• Currently use sildenafil

Exclusion Criteria:

• Other primary sexual disorders
• History of radical prostatectomy or other pelvic surgery that affected being able to have an erection
• History of penile implant or clinically significant penile deformity.
• Nitrate use
• Certain heart problems