SWitching to Abilify Trial (SWAT)

Inclusion Criteria: * Signed written informed consent * Men and women, ages 18 to 65. Women of childbearing potential (WOCBP) must be using an adequate method of contraception to avoid pregnancy throughout the study in such a manner that the risk of pregnancy is minimized. * Patients who have not been hospitalized during last three months * Patients who have kept clinically stable dosage during last one month * Patients with a diagnosis of schizophrenia and schizoaffective disorder as defined by DSM-IV criteria * Patients whose symptoms are not optimally controlled or whose antipsychotic medication is not well-tolerated, which in the clinical judgment of the treating psychiatrist require a change of treatment. * Patients who have received antipsychotics in the past must have shown a response to a neuroleptic medication other than clozapine. Exclusion Criteria: * Patients who are unwilling or unable to use an acceptable method to avoid pregnancy for the entire study period * Women who are pregnant or breastfeeding * Patients who are at risk for committing suicide: either having active suicidal ideation considered clinically significant or recently attempted suicide * Patients with a diagnosis of bipolar disorder, depression with psychotic symptoms, or organic brain syndromes * Patients who have met DSM-IV criteria for any significant Psychoactive Substance Use Disorder within the 3 months prior to Screening * Patients considered treatment-resistant to antipsychotic medication (patients need to have shown a previous response to a antipsychotic medication other than clozapine) and patients with a significant history of intolerance to multiple antipsychotic treatments * Treatment with a long-acting antipsychotic (i.e., haloperidol decanoate or fluphenazine decanoate) in which the last dose was within 3 weeks of randomization. * Patients with a history of neuroleptic malignant syndrome * Patients with epilepsy, a history of seizures (except for a single childhood febrile seizure), or a history of an abnormal EEG, severe head trauma, or stroke or who have a history or evidence of other medical conditions (e.g., congestive heart failure) that would expose them to an undue risk of a significant adverse event or interfere with assessments of safety or efficacy during the course of the trial * Patients who would be likely to require prohibited concomitant therapy during the trial * Patients who have previously enrolled in an aripiprazole clinical study or who have participated in any clinical trial with an investigational agent within the past month * Prisoners or subjects who are compulsorily detained for treatment of either a psychiatric or physical (e.g., infectious disease) illness must not be enrolled into this study.