The focus of most previous research concerning tardive dyskinesia has been on the impact of risk factors on the development( incidence) of this syndrome. In this paper, we report our results on the relationship between risk factors and the severity of tardive dyskinesia. A total of 33 patients diagnosed as tardive dyskinesia with no other medical illness studied: 21 males and 12 females with a mean age of 50. Twenty four of them diagnosed as schizophrenia and 9 as mood disorder, assessment of severity of tardive dyskinesia was based on the AIMS score. Significant positive correlations were found between age, sex, primary mental illness and severity of tardive dyskinesia.