Chronic administration of iminodipropionitrile causes a persistent behavioral syndrome which is characterized by lateral and vertical head shakes, random circling, hyperactivity and increased acoustic startle response in rodents. These behavioral abnormalities are similar to those observed after the acute administration of serotonin (5-HT) and dopamine (DA) agonists, and of some peptides including thyrotropin-releasing hormone (TRH) and the enkephalins. The data available so far indicate that the 5-HT system which interacts with some other neurotransmitters such as DA and norepinephrine (NE) in both reciprocal and nonreciprocal ways may be primarily involved in the manifestations of this persistent dyskinetic syndrome. Preliminary evaluation of the peptidergic systems has also revealed possible involvement of opiate peptides in the IDPN-induced dyskinetic phenomena. More studies are needed to assess the role of specific molecular events which may occur at cortical, subcortical, and/or spinal levels to cause this interesting psychomotor syndrome.