• Secondary objectives are to evaluate additional metabolic endpoints [ Time Frame: From baseline to endpoint. Endpoint is at 6 month, but can be earlier in case of early withdrawal ] [ Designated as safety issue: No ]
• Demonstrate non-inferiority of paliperidone ER versus olanzapine in efficacy as measured by Positive and Negative Syndrome Scale (PANSS). [ Time Frame: From baseline to endpoint. Endpoint is at 6 month, but can be earlier in case of early withdrawal ] [ Designated as safety issue: No ]

The purpose of this 6 month study is to compare the metabolic effects of paliperidone ER and olanzapine in patients with schizophrenia, using the ratio of the concentration of lipids (triglycerides) in the blood to the concentration of good cholesterol (high density lipoproteins; HDL) in the blood as the primary parameter. Approximately 456 adult patients will participate in this study.

This is a prospective randomized (study medication is assigned by change) open-label, parallel-group, multicenter, 6 month study to compare the metabolic effects of paliperidone ER and olanzapine in patients with schizophrenia using the ratio of the concentration of lipids (triglycerides) in the blood to the concentration of good cholesterol (high density lipoproteins; HDL) as the primary parameter. Secondary objectives include evaluation of additional parameters related to the total of the actions of the body to keep it alive (metabolic endpoints) and demonstration of non-inferiority of paliperidone ER versus olanzapine in efficacy as measured by Positive and Negative Syndrome Scale (PANSS). Patients previously treated with any oral antipsychotic, except those treated with paliperidone ER, olanzapine or clozapine during the last 6 months, can be enrolled and will be treated with paliperidone ER (6 to 9 mg/day) or olanzapine (10 to 15 mg/day). Patients will be divided into groups according to the metabolic effects of their previous antipsychotic medication (medication that does not increase body weight vs. medication that increases body weight). Throughout the study flexible dosing is allowed based on the investigator's discretion. A study treatment period of 6 months is planned for all patients. Medication to treat symptoms like confusion, blurred vision, constipation, dry mouth, light-headedness, difficulty starting and continuing to urinate, and loss of bladder control may continue up to four weeks and should then be tapered off at the discretion of the investigator. Approximately 456 adult patients (228 in each treatment group) will participate in this study. Efficacy will be assessed with the following measures: PANSS (total score and subscale scores), CGI-S, Self-rated health status Survey SF-36, and Sleep and daytime drowsiness evaluation scale. The parameters related to the total of the actions of the body to keep it alive (metabolic endpoints) will be assessed with the following: ratio of blood lipids to blood good cholesterol concentrations (triglycerides/HDL) (for this primary evaluation, plasma fasting lipids and good cholesterol concentrations will be measured), fasting plasma insulin and fasting plasma glucose, plasma glucose and insulin concentrations before and after a 75 gram oral glucose tolerance test to asses insulin sensitivity and changes in insulin secretion, fasting good cholesterol, lipids, and glucose levels for the determination of new onset or presence of metabolic syndrome during treatment according to criteria of the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (NCEP/ATPIII criteria), weight, Body-Mass-Index and waist circumference for the determination of new onset or presence of a medical condition associated with abdominal obesity, abnormalities in glucose, lipid and cholesterol metabolism, and elevated blood pressure that increases the risk of cardiovascular disease and type 2 diabetes (metabolic syndrome) during treatment according to NCEP/ATP III criteria. All patients who receive trial medication (paliperidone ER or olanzapine) at least once will be included in the analysis of the demographic and baseline characteristic data. 2 dosage levels of paliperidone ER (6 or 9mg per day) and 2 of olanzapine (10 and 15mg per day) are available to the patients. Throughout the study flexible dosing is allowed based on the investigator's discretion. Study medication is to be taken in the morning orally, with water. A study treatment period of 6 months is planned for all patients.

• Drug: paliperidone ER
• Drug: olanzapine

Inclusion Criteria:

• Patient meets the DSM-IV criteria for schizophrenia
• Patient has a PANSS total score at screening of 60 to 100, inclusive
• Patient must, in the opinion of the investigator, benefit from treatment with paliperidone ER or olanzapine
• Patients on lipid-lowering therapy must be on a stable dose for at least 4 weeks for statins, niacin, ezetimibe and resins or for at least 12 weeks for fibrates
• Female patients must be postmenopausal (for at least 1 year), surgically sterile, abstinent, or, if sexually active, be practicing and effective method of birth control (e.g. prescription oral contraceptives, contraceptive injections, intrauterine device, double-barrier method, contraceptive patch, male partner sterilization) before entry and throughout the study
• Women of child-bearing potential must have a negative urine pregnancy test at screening
• Patient is healthy on the basis of a physical examination and vital signs at screening

Exclusion Criteria:

• Patient has previously been treated with paliperidone ER, olanzapine, or clozapine within the past 6 months or has never been treated with an antipsychotic before
• Treatment with a depot antipsychotic within the past 3 months
• Treatment with a mood stabilizer or a recently initiated antidepressant (<= 3 months)
• Patient has abnormal fasting plasma glucose (> 126 mg/dL) or fasting triglycerides (TG) levels (> 400 mg/dL) at screening
• Relevant history of any significant and/or unstable cardiovascular, respiratory, neurologic (including seizures or significant cerebrovascular), renal, hepatic, endocrine, or immunologic diseases, including recent or present clinically relevant laboratory abnormalities (as deemed by the investigator)
• History or current symptoms of tardive dyskinesia
• History of neuroleptic malignant syndrome
• Pregnant or breast-feeding female