Evaluate the safety, tolerability and pharmacokinetics of ABT-288 in order to determine the maximum tolerated dose of ABT-288 in stable schizophrenic volunteers receiving treatment with an atypical antipsychotic.

Inclusion Criteria:

• Subject has signed informed consent;
• Current DSM-IV-TR diagnosis of schizophrenia;
• Clinically stable on the same single second-generation antipsychotic for the past 8 weeks;
• Meets study-specific PANSS criteria;
• Willing and able to cooperate with cognitive testing
• Females are not pregnant, not breast-feeding;
• Females are post-menopausal or surgically sterile or practicing birth control;
• Males are surgically sterile or agree to be sexually inactive or use barrier method of birth control

Exclusion Criteria:

• Subject has a substance dependence disorder that has not been in sustained remission for at least 1 year;
• Diagnosis of schizoaffective disorder;
• Bipolar disorder, manic episode, dementia, OCD, or drug-induced psychosis or current major depressive disorder;
• Diagnoses with mental retardation; acute psychosis hospitalization within past 6 months;
• Current clozapine treatment; suicidal ideation or behavior;
• BMI of 39 or greater; current homicidal or violent ideation;
• Medical or CNS condition other than schizophrenia that could affect cognitive performance or testing; relevant drug sensitivity or allergy; positive urine screen for alcohol or drugs of abuse;
• Positive hepatitis or HIV test result;
• Recent clinically significant illness/infection or surgery;
• Recent blood product transfusion, donation or loss of 5 mL/kg of blood;
• Visual, hearing or communication disability