Although it is believed that tardive dyskinesia (TD) is reversible in its early stages, little is known about the long-term effects of the subsequent administration of neuroleptics (NLP). Twenty cases of TD (four men and 16 women, aged 35 to 84, mean 52) who had first been diagnosed between 1968 and 1976, were followed up for an average of 10 years. By 1983, in nine cases (including one patient who died), TD had disappeared; it persisted in six cases (one patient died), and recurred following remission in five (two patients died). After the onset of TD, the administration of NLP was discontinued in eight cases, decreased in six, maintained at the same level in four and increased in two. In most patients whose age at onset was below 60, TD was reversible regardless of the NLP administration pattern. On the other hand, TD persisted in most cases in which the onset age was 60 or more, despite the large numbers in which NLP was discontinued. Nevertheless, recurrence of TD was occasionally observed among the reversible cases, and, in two of these, the condition became persistent. It is, therefore, speculated that the long-term outcome of TD is determined mainly by the age at onset. However, if the continued administration of NLP is combined with aging, reversible TD observed among young patients may recur or become persistent.