The diagnosis of ED and the determination of its severity requires a comprehensive analysis, combining the subjective description of the man with the results of the hospital examination. The vast majority of men who experience erectile difficulties are concerned about this issue because it is directly related to the difficulty of treatment, the cost of treatment and the degree of recovery. This is a question that requires a combination of a man’s subjective description and the results of a hospital examination. The doctor will first ask about the condition and have the man fill out an erectile function self-measurement form. Each question on the form is rated according to the severity of the problem in the answer sheet of his choice, with a score from 0 to 5, the lower the score, the more severe the condition. (≤7 points: severe; 8 to 11 points: moderate; 12 to 16 points: mild; 17 to 21 points: mild; ≥22 points: normal). After asking about the condition, the doctor will perform some targeted examinations, such as: the condition of external genitalia; endocrine condition; systemic diseases including cardiovascular disease, hypertension, diabetes, liver and kidney dysfunction, etc. If necessary, some special tests are needed including: (1) nocturnal penile erection test; (2) penile cavernosal injection vasoactive drug test; (3) penile color ultrasound, Doppler examination; (4) penile cavernosal perfusion angiography, cavernosal manometry if necessary; (5) selective penile arteriography, etc. Not every one of the above tests is performed, especially the special tests are only for men with special conditions, so there is no need to worry that going to the hospital for the tests will be troublesome. Combining the results of questionnaires and tests, doctors can generally tell men clearly whether ED exists, and if it does, doctors will determine roughly what the nature and severity of the ED is, so that men can get reasonable and effective treatment.