The introduction of PDE 5 inhibitors has widen the ambit of health care in erectile dysfunction (ED), which now includes family doctors, urologists, endocrinologists, neurologists, angio-cardiologists, psychiatrists, psychologists and other specialists. To make a proper diagnosis, it is convenient to know there are many diseases associated with ED. To evaluate ED we have to identify sexual problems and to use certain means, such as adequate questionnaires and symptom scores, a detailed sexual and clinical history, physical exam and elementary lab tests. In most cases of ED it is not necessary to perform invasive tests or refer the patient to a specialist, but the doctor needs to know there are cases that require such reference, and sometimes more studies and tests are required.