The serendipitous discovery that inhibiting type 5 phosphodiesterase (PDE5) using sildenafil, a potent PDE5 inhibitor (PDE5i) initially developed for cardioprotection, introduced the possibility of orally managing erectile dysfunction (ED) led to an increase in research data, which are currently considered groundbreaking for the new discipline of sexual medicine. Here, PDE5A is linked to erectile dysfunction.