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