Galantamine acts on acetylcholinesterase, and has been shown to effectively treat cognitive symptoms in patients with Alzheimer's disease. Previous cellular research of nicotinic receptors has shown promising results, and it is theorized that the nicotinic system of patients with schizophrenia may be abnormal and may play an important role in the cognitive symptoms associated with schizophrenia. It is also postulated that galantamine may improve neuropsychiatric symptoms such as hallucinations, delusions, and apathy in patients with Alzheimer's disease. Atypical antipsychotic medications are effective treatment for schizophrenia patients but some symptoms remain. Therefore, galantamine may be a useful cotreatment for schizophrenia patients on atypical antipsychotic treatment. This is a pilot dose-ranging, randomized (patients are assigned different treatments based on chance), double-blind (neither the patient nor the physician knows whether drug or placebo is being taken, or at what dosage), placebo-controlled multicenter study that examines the effects of taking extended-release galantamine hydrobromide (16 or 24 mg once daily) or placebo on the effectiveness in reducing symptoms of schizophrenia patients who are already taking an atypical antipsychotic medication. The safety of combined treatment is also examined. Measures of effectiveness include the Positive and Negative Syndrome Scale (PANSS) to measure neuropsychiatric symptoms of schizophrenia; the Clinical Global Impression (CGI) scale to measure change over the course of the study; the Brief Assessment of Cognition in Schizophrenia (BACS) for verbal memory and learning, working memory, motor function, attention, verbal fluency, and executive functioning; the Continuous Performance Test (CPT) for sustained attention and distractability; reaction time test (RTT) and finger tapping test (FTT) for psychomotor speed; Lexical and Semantic Fluency Test (LSFT) for language skills. As schizophrenia patients are a population with high nicotine use, and galantamine may act on nicotine receptors, blood levels of nicotine are also measured as varying nicotine levels could alter the effects of galantamine. The null hypothesis that there is no difference between the 2 groups (galantamine cotreatment and placebo) will be tested for each of the efficacy measurements (total PANSS, BACS, and CGI scores) at Week 8. Measures of safety include physical examinations, electrocardiograms (ECGs), clinical laboratory tests, measurement of plasma prolactin concentrations, pregnancy test for women, and incidence of adverse events. Adverse events that might be related to the medications are also monitored using the Simpson-Angus Extrapyramidal Side Effects Scale (SAS), the Barnes Akathisia Rating Scale (BARS), and the Abnormal Involuntary Movement Scale (AIMS). Extended-release galantamine hydrobromide or matching placebo capsules for once-daily dosing. Patients take 8 milligrams (mg) per day during Week 1, 16 mg per day during Week 2, and 16 mg or 24 mg per day (depending on randomization) during Weeks 3 to 8. Treatment groups are placebo capsule, 16 mg capsule, 24 mg capsule.