Small fibre neuropathies (SFNs) are common and can significantly affect patients' lives due to debilitating pain and autonomic symptoms. We explain the tests that neurologists can use to diagnose SFNs and how neurophysiologists perform and interpret them. This review focuses on neurophysiological tests that can be used to investigate SFNs, their sensitivity, specificity and limitations. Some of these tests are available only in specialist centres. However, newer technologies are emerging from scientific research that may make it easier to diagnose these conditions in the future.