This is a two part study designed to evaluate the safety and efficacy of SB-773812 in the treatment of acute schizophrenia. Subjects with acute schizophrenia will be randomized in an adaptive design study to receive placebo, SB-773812 60mg or olanzapine 15mg for 12 weeks in Part A. An interim analysis will be conducted to assess the efficacy and safety of the SB-773812 60mg dose compared with placebo. Based on these data, up to two further doses of SB-773812 will be added to the randomization for Part B.

Inclusion Criteria:

• Meets the diagnostic criteria for schizophrenia as defined in DSM-IV.
• PANSS total score of at least 70 at Screen and Baseline and a minimum score of 4 (moderate) on at least 2 of the following: conceptual disorganization (P2) hallucinatory behaviour (P3) suspiciousness (P6) or unusual thought content (G9) at the Screen and Baseline visits

Exclusion Criteria:

• Subjects with a history of epilepsy or other seizure disorder, first episode of schizophrenia or other psychotic disorders (e.g. residual type schizophrenia, schizophreniform disorder, schizoaffective disorder, delusional disorder, etc.)
• Bipolar disorder, a history of substance dependence, or a medical or psychiatric disorder that would interfere with the accurate assessment of safety or efficacy are not eligible.