- Background: The pathogenesis of neuroleptic-induced tardive movement disorders (TMD), including tardive parkinsonism and tardive dyskinesia (TD), has not yet been established. An elevated serum level of total homocysteinehas been implicated as a risk factor for various neuropathologic states and some movement disorders. The aim of our study was to determine whether there is an association between serum total homocysteine level and the presence of TMD among schizophrenic and schizoaffective patients. Method: This study was conducted in Be'er Sheva Mental Health Center from August 2002 to May 2004. Fifty-eight patients with schizophrenia or schizoaffective disorder (DSM-IV) and TMD for at least 1 year (38 men, 20 women; age range, 28-73 years) were compared to a control group of 188 patients with DSM-IV-diagnosed schizophrenia or schizoaffective disorder without TMD (123 men, 65 women; age range, 19-66 years) regarding serum total homocysteine levels. Results: Men with TMD (demonstrating tardive parkinsonism and/or TD) had significantly higher mean serum total homocysteine levels compared to sex- and age group-matched controls. The difference between groups was almost entirely attributable to the homocysteine levels of young male patients (age group, 19-40 years old) with TMD. Conclusion: High serum total homocysteine level may constitute a risk factor for certain variants of TMD, especially in young schizophrenic or schizoaffective male patients. Further prospective studies are needed to clarify these findings.