The facial nerve has a complicated course from the brainstem to the periphery. It not only contains motor, but also secretory, sensory, and sensitive fibres. Thus, the functional measure of symptoms can be multi-faceted. The nerve is not directly accessible over an extensive distance because of its long course through the temporal bone. Therefore, diagnostics of nerve function and the differential diagnostics of its diseases could be a great challenge for the otolaryngologist. In this review, the most important methods for clinical examination, electrodiagnostics, and modern imaging techniques are critically surveyed. In addition, the significance of facial nerve monitoring for surgery in the cerebello-pontine angle, parotid surgery, and ear surgery is presented.