Based on specific, objective, and reproducible criteria, a classification scheme for trigeminal neuralgia (TN) and related facial pain syndromes is proposed. Such a classification scheme is based on information provided in the patient's history and incorporates seven diagnostic criteria, as follows. 1) and 2) Trigeminal neuralgia Types 1 and 2 (TN1 and TN2) refer to idiopathic, spontaneous facial pain that is either predominantly episodic (as in TN1) or constant (as in TN2) in nature. 3) Trigeminal neuropathic pain results from unintentional injury to the trigeminal nerve from trauma or surgery. 4) Trigeminal deafferentation pain results from intentional injury to the nerve by peripheral nerve ablation, gangliolysis, or rhizotomy in an attempt to treat either TN or other related facial pain. 5) Symptomatic TN results from multiple sclerosis. 6) Postherpetic TN follows a cutaneous herpes zoster outbreak in the trigeminal distribution. 7) The category of atypical facial pain is reserved for facial pain secondary to a somatoform pain disorder and requires psychological testing for diagnostic confirmation. The purpose of a classification scheme like this is to advocate a more rigorous, standardized natural history and outcome studies for TN and related facial pain syndromes.