Questionnaires are used within urology to objectify disease burden and symptom changes during therapy. Recent technological improvements, as the smartphone and tablet, create new fill-out possibilities. However, questionnaires are only validated on paper. In order to use questionnaires for multiple platforms, electronic validation is needed. The International Prostate Symptom Score has already been validated on the smartphone. The International Index of Erectile Function (normal version of 15 questions and short version of 5 questions) is widely used within urology, however electronic validation is required for usage on electronic platforms in the future.

Inclusion criteria:

• Male patients, ≥40 years of age, presenting at the outpatient clinic of Urology of the Academic Medical Center in Amsterdam.
• In possession of a smartphone, tablet or laptop/computer with internet connection.
• Access to email.
• Fluent speaking and reading the Dutch language.

Exclusion criteria:

• Change in treatment, especially erectile dysfunction at consultation which could impact the short term IIEF outcome during the cross-over time.
• Unable to provide informed consent.
• Unfit according to the medical doctor (for example cognitive problems, leading to inadequate follow-up of instructions).

Participants will be included at the outpatient clinic of the urology department at the Academic Medical Center in Amsterdam.