The effects of 3 cyclohexylamines were studied in a patient with thalamic pain. The compounds tested were the mono-hydrochlorides of, respectively, 1-phenylcyclohexylamine (CI 401), N-ethyl-l-phenylcyclohexylamine (CI 400), and l-(l-phenylcyclohexyl) piperidine (CI 395). In this patient, CI 401 caused leukopenia and uremia in only 8 days; when CI 400 was given for over a month, borderline azotemia and eeg changes were found. Both of these agents seemed to lessen the pain. CI 395 given for 5 months did control effectively the thalamic pain without recurrence after its withdrawal. However, termination of its use was necessitated by an acute delirioid reaction with some residual brain damage. Published experiences of others were reviewed; these drugs are not indicated in anesthesia due to unpredictability of response and a high incidence of psychic side effects. Their use as psychopharmacologic agents is not indicated due to lack of proved efficacy and their toxicity. It is concluded that these cyclohexylamines may provide an effective but hazardous treatment for thalamic pain and that their use is warranted in this disorder with appropriate safeguards.