Introduction: Autonomic dysfunction occurs in patients with central and peripheral nervous system diseases. It is important to quantify the sympathetic and parasympathetic involvement for the diagnosis of the autonomic failure, for follow up and evaluate the response to a specific treatment. The most important studies are cardiovascular and sudomotor functional tests. There are other tests for the study of autonomic dysfunction in different organs, that are specific to respectively medical specialty. Development: we describe main symptoms, functional autonomic tests and other methods to study cardiovascular: sympathetic vasomotor (noradrenergic) and cardiovagal (cholinergic) and sudomotor: sympathetic (cholinergic) functions. We describe symptoms and tests for assessment pupillary, genitourinary and gastrointestinal autonomic dysfunction. The indications for autonomic function testing in the different clinical scenarios are reported. Conclusions: combined evaluation of clinical and tests of autonomic function results allow to obtain the level and severity of autonomic dysfunction based upon pathophysiological support.