To gain knowledge about the effects of Cialis, researchers asked men a series of questions about the ability to achieve erections and the ability to maintain an erection after penetration during each attempt at sexual intercourse. These men were also asked questions about orgasms, desire, satisfaction with intercourse, and overall sexual satisfaction. Improvements in erections were somewhat based on the Cialis dosage. Men reported an improvement in erection enough to allow vaginal penetration up to 57 percent of the time with Cialis 5 mg, up to 77 percent of the time with Cialis 10 mg, and up to 85 percent of the time with Cialis 20 mg. In 33 to 75 percent of all cases (depending on the study), erections lasted long enough for successful intercourse.