A Study of QT and QTc Intervals in Patients Administered Immediate Release Paliperidone

Inclusion Criteria: * Patients must have a diagnosis of schizophrenia or schizoaffective disorder as defined by DSM-IV criteria, with no exacerbation of psychosis for at least 3 months prior to screening * Patients must have a normal 12-lead ECG at screening and on Day -1, including: Normal sinus rhythm (heart rate between 50 and 100 beats per minute) * QTcB interval \< = 430 msec for men, \< = 450 msec for women * QRS interval \<110 msec, PR interval \< 200 msec * Patients must weigh \> = 50 kg ( \> = 110 lb), with a body mass index \> = 18 and \< = 35 kg/m2 * Female patients must be postmenopausal (for at least 1 year), surgically sterile, or practicing an effective non-hormonal method of birth control (e.g., intrauterine device, double-barrier method, male partner sterilization, abstinence) before entry and throughout the study * must have a negative serum beta human chorionic gonadotropin pregnancy test at screening * and must have a negative urine pregnancy test within 24 hours before Day 1 of the randomization period. Exclusion Criteria: * Patient meets DSM-IV criteria for psychoactive substance dependence in the 3 months prior to screening * Patient is at risk for suicidal or violent behavior, as judged by the investigator: Patient has a clinically significant abnormality on ECG at screening or on Day -1 of the study * Patient has a heart rhythm disturbance that is known or suggested by history or that is demonstrated on ECG at screening * Patient has a blood pressure outside of the normal range (supine systolic blood pressure \<90 or \>140 mmHg and/or diastolic blood pressure \<60 or \> 90 mmHg) * Patient has unusual T-wave morphology in a majority of leads of the ECG (such as bifid T waves, low T waves) or prominent U waves at screening: Patient has a history of additional risk factors for torsade de pointes, such as heart failure, hypokalemia, family history of known long QT interval syndrome, or sudden unexplained death at a young age ( \< = 40 years) in a first-degree relative (i.e., biological parent, sibling, or offspring) * Patient has a relevant history of any significant and/or unstable cardiovascular, respiratory (including bronchial asthma), neurologic (including seizures or significant cerebrovascular disease), renal, hepatic, endocrine, immunologic, ophthalmologic, hematological, or other systemic disease.