Inclusion Criteria:

• Schizophrenia or Schizoaffective disorder, any subtype.
• Age 18-65 years
• Treated with ziprasidone at a dose of 160 mg/d for at least 3 weeks with adequate compliance.
• Concomitant standing or prn medications (except other antipsychotics and those noted as contraindicated in the ziprasidone package insert) are permitted during all treatment phases if they were present at a stable dose for at least 6 weeks prior to the start of initial ziprasidone treatment.
• A score of 4 (moderate) or greater on any of the 7 items of the PANSS Positive Symptom Subscale.
• Clinical judgment by the investigator that doses higher than 160 mg/day are warranted due to suboptimal clinical outcome despite adequate treatment at that dose
• Patient is judged capable of understanding all relevant risks and potential benefits of the study and has signed informed consent.
• Comorbid axis 1 conditions (including anxiety disorders, eating disorders, impulse control disorders) are permitted if they have been stable and have not been a primary focus of treatment over the previous 6 months.

Exclusion Criteria:

• Past or current intolerance of ziprasidone side effects.
• Presence of significant cardiac disease, including uncompensated congestive heart failure, myocardial infarction within the past 6 months or known history of congenital long QT syndrome.
• QTc greater than or equal to 500 msec.
• Serum potassium and magnesium concentrations outside of normal limits.
• Currently taking any medications which may affect cardiac conduction.
• Presence of any unstable or untreated medical disorder. Any history of seizures or seizure disorder other than febrile seizures of childhood; history of positive hepatitis B surface antigen; any subject who is HIV + or has diagnosis of AIDS. Any abnormal laboratory test that is judged to be clinically significant by the investigator.
• History of NMS), hypersensitivity or allergic response to antipsychotic therapy, including ziprasidone
• History of clozapine treatment for refractory psychotic symptoms
• Alcohol or substance dependence within the past 12 months or abuse within the past 3 months. Any subject with positive urine toxicology or alcohol use that is considered abnormal at baseline.
• Clinically significant suicidal or homicidal behavior or attempts within past 6 months.
• Any subject judged by the investigator to present a danger to self or others.
• Women of childbearing potential who are not using adequate contraception (oral contraceptives, barrier methods or who are clearly abstinent).
• Pregnancy or breast-feeding.
• Any subject who is judged by the investigator to be unable or unlikely to comply with all study requirements, including adherence with prescribed medication regimen.