A Study of RO4917838 in Patients With Sub-optimally Controlled Symptoms of Schizophrenia (NN25307)

Inclusion Criteria: * Adult patients, \>/= 18 years of age * Diagnosis of schizophrenia * Clinical stability for 16 weeks (4 months) prior to randomization * Antipsychotic treatment stability for the past 12 weeks prior to randomization * With the exception of clozapine, patients are on any of the available marketed atypical or typical antipsychotic (treatment with a maximum of two antipsychotics) Exclusion Criteria: * Has treatment resistant schizophrenia as judged by the treating physician OR have failed two trials * Evidence that patient has clinically significant uncontrolled or unstable medical disorder (e.g. cardiovascular, renal hepatic, gastrointestinal, hematologic, immunological, neurological, endocrine, metabolic or pulmonary disease) * Patient has a body mass index (BMI) of \<17 or \>40 kg/m2, respectively * Diagnosis of mental retardation or severe organic brain syndromes * In the investigator's judgment, a significant risk of suicide or violent behavior