This chapter has been written with a purpose of introducing the concept of paroxysmal dyskinesias in movement disorders to the reader. Unless the clinician is aware of this type of episodic illness, most of the times theses are considered as psychogenic or epileptic disorders. Though underlying pathophysiology is not still clear, in paroxysmal dyskinesia consciousness and EEG activities are usually preserved. It is well known that in the same family, various members may suffer from either epilepsy, paroxysmal dyskinesia or episodic ataxia indicating that clinical expression of underlying genetic defect is possibly site dependent; for example, excitation in cortex probably produces seizures, that of basal ganglia produces dystonia and that within cerebellum induces ataxia. The internist should particularly pay attention to this condition, as many medical conditions may first appear as paroxysmal disorders and mistaken as functional disorders.