Between October 1981 and September 1989, 564 patients admitted to the Department of Psychiatry of the Hospital of Oita Medical University received antipsychotic treatment. Ten (1.8%) of these patients developed neuroleptic malignant syndrome. This incidence is significantly greater than that reported in a group of other studies (27/17,811, 0.2%). We compared the characteristics of this sample with known risk factors for neuroleptic malignant syndrome. It is possible that Japanese people are at an increased risk for developing neuroleptic malignant syndrome. Psychomotor excitement, refusal of food, a weight loss of greater than 1 kg per week and oral administration of haloperidol at 15 mg/day or above were found to be risk factors for developing the neuroleptic malignant syndrome.