METHOD:A structured clinical interview, for DSM-IV Axis I Disorder, Patient Edition, was used to diagnose schizophrenia according to DSM-IV. Three hundred fifty patients were studied. The patients were then randomly divided into two groups on 175 subjects in each group. First group patients received either haloperidol deaconate 50 mg in weekly intramuscular and lamotrigine 150-200 mg in day per so for 12 weeks. Second group patients were given haloperidol deaconate 50 mg in weekly intramuscular and placebo per os for 12 weeks. Data for clinical assessments were collected at weeks 0, 6 and 12 weeks. The expressiveness of psychopathology was estimated on PANSS. Test response in both groups was defined as a reduction in the PANSS by using analysis of variance and chi-square tests.