Assess the effect of daily treatment of vardenafil 20mg or sildenafil 100mg and placebo on sperm function

Inclusion Criteria:

• Healthy male subjects or men with ED aged 25 - 64
• Baseline sperm conc. of > 20 mio / ml- Normal World Health Organization A+B+C sperm mortality > 50%- Normal sperm morphology (WHO, 1992 manual criteria) > 30% and - 1.0 mL ejaculate volume at each of the 3 analyses during the screening phase.

Exclusion Criteria:

• Presence of any psychological or physiological abnormalities that in the opinion of the Investigator would significantly impair sexual performance or ability to provide semen samples according to the protocol- Spinal cord injury
• History of surgical prostatectomy
• Other exclusion criteria apply according to US Product Information