A Study Comparing the Efficacy and Tolerability of Ziprasidone vs. Clozapine for the Treatment of Schizophrenia in Patients Who Continue to Have Symptoms on or Cannot Tolerate Other Antipsychotic Drugs

- Patients with a history of myeloproliferative diseases, history of granulocytopenia,
agranulocytosis due to a drug

- Diagnosis of substance dependence within previous 3 months using DSM-IV criteria

- History of seizure

- Organic mental disease, including mental retardation or epilepsy