The discovery of sildenafil, a selective PDE-5 inhibitor, led to several basic studies that showed that this type of enzyme controls the cavernous tissue, ensuring the selectivity of the drug. It should be noted that these studies also elucidated the mechanisms of action of other drugs that have been used in clinical practice for a long time, in particular papaverine and erectile dysfunction, and significantly expanded the range of knowledge about the mechanism of erection and its effects. disorders leading to impotence. The appearance of sildenafil has also had a significant impact on clinical research in the field of sexual medicine. In recent years, terminology has been clarified and new definitions have been developed for various forms of sexual disorders. Sildenafil clinical trials prompted the creation of new diaries and questionnaires to assess the status of male sexual function. Analysis of the demographics of participants in large-scale clinical trials revealed risk factors for erectile dysfunction, which in turn contributed to the understanding of its etiology.