Bacillary dysentery, an acute infection caused by various strains of Shigella, is characterized by abdominal pain, tenesmus, and diarrhea with mucus, pus and blood. Neurologic manifestations including meningismus, delirium and convulsions may accompany the infection. We describe a thirteen-year-old girl who presented with headache, convulsion and loss of consciousness at the onset and developed diarrhea with blood and pus after hospitalization. The diagnosis of shigellosis was based on clinical data and isolation of the microorganism in the stool specimen. After improved physical functions, the patient developed mutism that continued for two days in the course of her illness, despite having no history of neurologic or psychological problems. She was diagnosed by a psychiatrist with organic mental syndrome NOS (Not Otherwise Specified) according to DSM-III-R criteria. None of the conditions that may cause mutism could be confirmed. This is the first reported case of mutism accompanying shigellosis.