Cognitive deficits have been considered as a core symptom domain of schizophrenia. Amelioration of or improvement in cognitive impairments is becoming an important focus of clinical treatment development. Varenicline is a potent and selective alpha 4 beta 2 nicotinic acetylcholine receptor partial agonist that has been developed for smoking cessation. In animal studies, alpha 4 beta 2 receptor agonists significantly improve working memory and attention function. Subjects will be assigned in 1:1 ratio to receive varenicline or placebo respectively. Assessments will be done using several neuropsychologic tests, clinical rating scale including assessment of nicotine withdrawal scales.Varenicline has been found to be efficacious for smoking cessation in the general population and animal studies have demonstrated the cognitive benefits of this agent. However, no published work is available evaluating the cognitive effects in humans. Thus, patients may experience improvements in cognitive function and in people who are smokers, these people may be able to achieve abstinence in smoking. This will in turn improve long-term functional outcomes and health outcomes in people with schizophrenia. This is an exciting opportunity for discovery if indeed cognitive abilities could be improved with this adjunctive treatment.