1. Find the early diagnostic markers of erectile dysfunction;
2. Study the warning role of ED in some diseases.

Inclusion Criteria:

1. Male and at least 18 years of age.
2. Provide signed informed consent.
3. Have a history of erectile dysfunction (ED: defined as a consistent change in the quality of erection that adversely affects the subject's satisfaction with sexual intercourse) .
4. Have a stable monogamous relationship with a female partner. To some subjects with poor sexual experience, re-evaluation would be conducted after a 4-weeks sex education.
5. Make at least four sexual intercourse attempts with the female sexual study partner during the 4-week therapeutic period without medication.
6. Agree not to use any other ED treatment for at least 4 weeks.

Exclusion Criteria:

1. severe diseases (such as congestive heart failure, arrhythmia, significant renal or hepatic dysfunction and anemia);
2. Had clinically noteworthy penile deformities, pelvic surgery or trauma of perineal region;
3. Had received long-term pharmacotherapy (including antioxidant agents, vitamins and traditional Chinese drugs).
4. An addiction problem (with a history of injection or administration of opium, poppy, heroin, hemp, morphine, cocaine, caffeine, ketamine and meperidine etc.)

men with erectile dysfunction healthy men general male population