This multi-center, randomized, double blind, parallel-group, placebo-controlled study will evaluate the efficacy and safety of RO4917838 (bitopertin) in patients with persistent, predominant negative symptoms of schizophrenia. Patients, on stable treatment with antipsychotics, will be randomized to receive daily oral doses of RO4917838 or matching placebo for 52 weeks, followed by an optional treatment extension for up to 3 years.

Inclusion Criteria:

• Adult patients, aged 18 years and above
• Diagnosis of schizophrenia of paranoid, disorganized, residual, undifferentiated or catatonic subtype
• Predominant negative symptoms
• With the exception of clozapine, patients are on any of the available marketed atypical or typical antipsychotics (treatment with a maximum of two antipsychotics)

Exclusion Criteria:

• Evidence that patient has clinically significant, uncontrolled and unstable disorder (e.g. cardiovascular, renal, hepatic disorder)
• Body Mass Index (BMI) of <17 or >40 kg/m2
• Depressive symptoms, defined as a score of 9 or greater on the Calgary Depression Rating Scale for Schizophrenia (CDSS)
• A severity score of 3 or greater on the Parkinsonism item of the ESRS-A (Clinical Global Impression, Parkinsonism)