Although tardive dyskinesia, a serious and sometimes irreversible side effect of antipsychotic drug use, is becoming increasingly common, there is still considerable confusion concerning the course of the syndrome. The authors observed 12 psychiatric patients with tardive dyskinesia from the inception of the syndrome. They found that first symptoms rarely persisted if antipsychotics were discontinued and concluded that the length of time symptoms have persisted prior to drug discontinuation, not age at onset, may be the major variable determining reversibility of the syndrome.