A method and a device for diagnosing the presence of nerve damage (polyneuropathy) in a subject or the degree of the polyneuropathy is distinguished in that the skin temperature on an extremity of the subject is increased, in that the perfusion value on this extremity or a value correlating thereto is simultaneously measured, and in that the time from onset of the increase in skin temperature to onset of an increase in perfusion due to the increased skin temperature is evaluated as a measure of the presence or the degree of the polyneuropathy.
