Cialis 20 mg Tablet belongs to the group of medicines called phosphodiesterase type 5 (PDE 5) inhibitors, primarily used to treat erectile dysfunction (impotence) and benign prostatic hyperplasia (BPH). Sometimes, Cialis 20 mg Tablet is also used to treat pulmonary arterial  hypertension (high blood pressure in the lungs). Erectile dysfunction is the inability to keep a hard and erect penis suitable for sexual activity. Benign prostatic hyperplasia, also called as prostate enlargement, is the non-cancerous growth of the prostate gland.