This open-label study is an extension of a 6-week randomized, double-blind, parallel-group study in which the effectiveness and safety of 4 different oral treatments administered once daily are compared in patients with schizophrenia: paliperidone 6 or 12 milligrams (mg), olanzapine 10 mg (an approved treatment for schizophrenia), or placebo. Following the double-blind treatment phase, eligible patients may enter this 52-week open-label extension with slow, extended-release paliperidone (with no comparison treatments). In the open-label extension, all patients, regardless of their randomized treatment in the double-blind phase, will begin on extended-release paliperidone 9 mg once daily. Thereafter, patients will be maintained on a flexible dosage of extended-release paliperidone throughout the 52-week study. The dosage may be increased or decreased within this range in accordance with the clinical judgment of the investigator, based on observations of patient response and tolerability. Because flexible dosing more closely mimics clinical practice, this design may provide more clinically relevant findings in the open-label setting.The final visit in the double-blind phase may serve as the initial visit for the open-label extension. Study visits will occur at Day 4 and then weekly for the first 4 weeks (Weeks 1, 2, 3, and 4) and then every 4 weeks through Week 52 or until early termination. Evaluations of the safety and effectiveness of extended-release paliperidone treatment will be performed at scheduled times throughout the open-label extension. Flexible dosage (3, 6, 9, or 12 milligrams (mg)) extended-release paliperidone tablets administered orally once daily for 52 weeks, following a 6-week double-blind study in which patients receive fixed oral doses of 6 mg or 12 mg extended-release paliperidone or olanzapine 10 mg.