Cialis 20 mg tablets are used to treat erectile dysfunction (ED), also called impotence, in men. Reduced blood flow can be caused by physical complications from an injury or illness, or certain psychological conditions such as anxiety, stress, depression, and more. Chronic lifestyle factors like smoking, drinking, and obesity. ED is strongly age-related, and the incidence of moderate to severe ED can increase threefold between the ages of 40 and 70 years.