Correct recognition of spontaneous linguobucco-facial dyskinesia is at least of interest in that it enables accurate evaluation of the impact of neuroleptic medication on the occurrence of similar neurological disorders. Since 1963, first anecdotal evidence and then series of cases of spontaneous dyskinesia have been reported. This has enabled evaluation of the prevalence of these disorders in subjects aged over 60 to be determined as 10% whereas incidence is over 50% in subjects of the same age receiving neuroleptics. Nonetheless, a number of uncertainties persist. Epidemiological studies produce very variable results suggesting that the concept of tardive dyskinesia is not always adequately defined and that certain disorders of a different type are sometimes confused with that condition. Dyskinetic movements involve the face and trunk, like those of chorea, but do not share the latters' abrupt rapid and unpredictable nature. Dyskinetic movements on the contrary, tend toward a degree of reproducibility, if not stereotypy, in the manner of ballistic movements which may be distinguished by their rotary character and the fact that they are generally localized in one half of the body. Lastly dyskinetic movements frequently have the creeping appearance of athetoid movements from which they may be distinguished by case history. The various characteristics confer a highly specific appearance on dyskinetic movements which was well described by Sigwald back in 1959. It should be stressed that author, who had already studied bucco-lingual dyskinesia in epidemic encephalitis in 1953, discovered, with surprise, the existence of such disorders in an infectious context.(ABSTRACT TRUNCATED AT 250 WORDS)