The primary objective of this study is to evaluate the change from baseline in the erectile function domain of the International Index of Erectile Function (IIEF-EF) scores in patients receiving 4 weekly treatments of shockwave therapy versus those receiving a sham treatment. The change will be evaluated at 3 months after the end of a sequence of 4 weekly treatments.

The secondary objectives of this study are:

A. To evaluate erectile function (EF) categorical improvement in patients receiving 4 weekly treatments of shockwave therapy versus those receiving a sham treatment, at 3 months after a first sequence of treatment.

B. To compare improvements in erectile function between 4 weeks of phosphodiesterase type 5 inhibitor (PDE5i) use and 4 weekly treatments of shockwave therapy ("within patient" effect).

C. To compare improvements in erectile function between 4 weeks of PDE5 inhibitor use and 4 weekly treatments of sham shock wave therapy ("within patient" effect).

D. To evaluate the effect of a 2nd sequence of 4-8 weekly shock wave treatments 3 months after this second sequence.

E. To evaluate treatment effects (the same comparisons as in objectives A, B, C, D) on other validated measure of EF (question 2 of the sexual encounter profile (SEP2), question 3 of the sexual encounter profile (SEP3), Global Assessment Question (GAQ), Erection Hardness Scale (EHS)), and the remaining domains of the IIEF score (orgasmic function, sexual desire, intercourse satisfaction, overall satisfaction), as well as the total IIEF score.

F. To evaluate treatment tolerance and potential adverse events. G. To compare changes in EF measures over time for a follow-up period of 12 months following the second sequence of 4 weekly shock wave treatments.

H. To compare the effect of a sequence of 4 weekly shock wave treatments versus 8 biweekly shock wave treatments 3 months after the treatment ("within patient" effect).

Inclusion Criteria:

• The patient has been correctly informed about the study.
• The patient must have given his informed and signed consent.
• The patient must be insured or beneficiary of a health insurance plan.
• The patient is a man between 18 and 80 years of age. (≥18 years and < 80 years)
• The patient has been in a stable sexual relationship for over 3 months
• The patient is consulting for erectile dysfunction lasting for over 6 months
• IIEF-EF6 score between 6 and 25
• Patients have at least a natural tumescence during sexual stimulation (EHS score ≥ 1)
• Pre-inclusion: Patient is willing to have 4 weeks of PDE5i treatment at the beginning of the trial, and then stop all treatment for an additional month.
• Pre-inclusion: The patient agrees to try to engage at least 3 sexual intercourses per month during this period
• Inclusion: Patient has completed 4 weeks of PDE5i treatment, and then stopped all treatment for an additional month.
• Patient is available for a follow up of 19 months (at time of pre-inclusion and then 17 months at time of inclusion)

Exclusion Criteria:

• The patient is participating in another interventional study
• Within the past three months, the patient has participated in another interventional study
• The patient is in an exclusion period determined by a previous study
• The patient is under judicial protection
• The patient is an adult under guardianship
• The patient refuses to sign the consent
• It is impossible to correctly inform the patient
• Complete anerection
• History of pelvic cancer surgery (radical prostatectomy, cystectomy, abdominoperineal resection of the rectum)
• Untreated testosterone deficiency
• Neurological disease affecting the central nervous system
• Untreated psychiatric disease, or psychiatric disease that may compromise study participation
• Anatomical malformation of the penis considered by the investigator as being able to prevent vaginal penetration
• Chronic haematological pathology associated with risk of haemorrhage
• Oral or injectable antiandrogen treatment
• The patient is taking blood thinners AND/OR has an International Normalized Ratio >3
• Known allergy to treatments used in the study (e.g. Cialis, gel)

Exclusion criteria: The patient has contraindications for Cialis as mentioned in the SPC, re-given here :

• Hypersensitivity to the active substance or to any of the excipients listed in section 6.1 of the SPC.
• In clinical studies, tadalafil was shown to augment the hypotensive effects of nitrates. This is thought to result from the combined effects of nitrates and tadalafil on the nitric oxide/cGMP pathway. Therefore, administration of CIALIS to patients who are using any form of organic nitrate is contraindicated. (see section 4.5 of the SPC).
• CIALIS, must not be used in men with cardiac disease for whom sexual activity is inadvisable. Physicians should consider the potential cardiac risk of sexual activity in patients with pre-existing cardiovascular disease.
• The following groups of patients with cardiovascular disease were not included in clinical trials and the use of tadalafil is therefore contraindicated:
• patients with myocardial infarction within the last 90 days,
• patients with unstable angina or angina occurring during sexual intercourse,
• patients with New York Heart Association Class 2 or greater heart failure in the last 6 months,
• patients with uncontrolled arrhythmias, hypotension (< 90/50 mm Hg), or uncontrolled
• uncontrolled hypertension,
• patients with a stroke within the last 6 months.
• CIALIS is contraindicated in patients who have loss of vision in one eye because of non-arteritic anterior ischaemic optic neuropathy (NAION), regardless of whether this episode was in connection or not with previous PDE5 inhibitor exposure (see section 4.4 of the SPC).