The purposes of this study are to determine:

• The effectiveness of olanzapine as compared to quetiapine in treating and preventing the recurrence of a variety of symptoms of schizophrenia and schizoaffective disorder in patients who are obese or overweight.
• The safety of olanzapine as compared to quetiapine.

Inclusion Criteria:

• You must be 18-75 years of age and be diagnosed with schizophrenia or schizoaffective disorder
• You must be able to visit the doctor's office thirteen (13) times over a twenty-six (26) week period

Exclusion Criteria:

• You are a woman and are pregnant or breastfeeding
• You have an acute or unstable medical illness, such as heart, liver, or kidney disease, or you have a seizure disorder. (Note: If you are uncertain about a particular condition, please discuss it with your physician.)
• You have a history of allergic reaction or intolerance to olanzapine or quetiapine