A Study for Patients With Erectile Dysfunction to Test Whether Tadalafil Taken Once a Day Can Better Improve Psychological Outcomes.

Inclusion Criteria:

• History of erectile dysfunction (ED).

• Have had satisfactory response to tadalafil, sildenafil citrate, or vardenafil HCl fora period of at least 6 months and expect frequent use (at least one dose per week, onaverage) when administered as needed.

• Have never used tadalafil 5 mg or 2.5 mg once a day therapy.

• Anticipate having the same adult female sexual partner willing to participate duringthe study.

• Agree to make at least four sexual intercourse attempts during the first four weeks ofthe study.

• Agree not to use any other treatment for ED (even herbal treatments) during the study.

• Agree to follow the directions given by the study doctor and staff about using thestudy drug.

Exclusion Criteria:

• Have any other primary sexual disorders present or penile deformity.

• Have history of radical prostatectomy or penile implant.

• Have problems with your kidneys, liver, or nervous system.

• Have uncontrolled diabetes, as measured by a blood test for haemoglobin A1C greaterthan a value of 11%.

• Are being treated for heart disease with any drug that is called a nitrate (forexample, nitroglycerin).

• Have chest pain (called unstable angina or angina) that requires treatment.

• Have heart disease that causes symptoms after you exert yourself.

• Have had any of the following in the past 90 days: Heart attack, also known as amyocardial infarction (MI); Heart bypass surgery (called coronary artery bypass graftsurgery); Had a procedure to open up blood vessels in the heart known as angioplastyor stent placement (percutaneous coronary intervention).

• Have a history of loss of vision in one eye because of nonarteritic anterior ischemicoptic neuropathy (NAION).

• Have retinitis pigmentosa.

• Have history of human immunodeficiency virus (HIV).

• Have very high or very low blood pressure (your study doctor will discuss the limitswith you).

• Have had a stroke or a significant injury to your brain or spinal cord within the last 6 months.

• Have rare hereditary problems of galactose intolerance, the Lapp lactase deficiency orglucose-galactose malabsorption Lactose intolerance.

• Have a scheduled or planned surgery requiring anaesthesia during the course of thestudy.

• Have a scheduled cataract surgery during the curse of the study.