Patient 1 was a 40-year-old man, who suffered from right leg myoclonus 1 week after an episode of fever and headache. Myoclonus disappeared 4 months after administration of clonazepam. Patient 2 was a 42-year-old man, who suffered from right leg myoclonus, attacks of speech arrest and a generalized tonic-clonic seizure. His symptoms disappeared after steroid-pulse therapy, but right leg myoclonus and episodic impairment of consciousness recurred within a month. He underwent another steroid-pulse therapy and his symptoms disappeared. In both patients, cerebrospinal fluid (CSF) study showed pleocytosis and elevated protein level, electrophysiological study showed cortical reflex by stimulation of the right tibial nerve, and brain MRI showed the high intensity area in the left parietal lobe. In addition, on electroencephalogram (EEG) spikes at vertex preceded myoclonic jerk of the right tibialis anterior muscle in both patients. These findings indicate that focal cortical reflex myoclonus was accompanied by acute central nervous system (CNS) infection. Furthermore, in both patients, autoantibody against glutamate receptor subunits ε2 was detected both in serum and CSF, which also suggest that autoimmune mechanism contributed in the pathophysiology of acute development of focal cortical reflex myoclonus.