Primitive (developmental) reflexes are present in fetal and infant life, but disappear in adulthood. Their elicitation in later life usually occurs in association with cortical or diffuse cerebral dysfunction and suggests a new approach to the issue of whether tardive dyskinesia is particularly likely to occur in patients with organic brain disorder(s). Sixty-six patients with schizophrenia (age range 50-86) and 18 with bipolar affective disorder (age range 40-77) were assessed for the presence of involuntary movements and for the release of the grasp, palmomental, snout, corneomandibular, and glabellar reflexes. In each diagnostic group, patients with involuntary movements showed a significant excess of primitive reflexes in comparison with otherwise indistinguishable patients without such movements. These results complement recent reports that similar patients with involuntary movements also show greater cognitive impairment and point anew to an association between the presence of tardive dyskinesia and of organic brain dysfunction. They raise again the issue of whether or not such dysfunction may be a consequence of neurodevelopmental abnormality rather than of neurodegenerative processes.