In this study, we will use magnetic resonance spectroscopy (MRS) to measure glutamate levels in prefrontal cortex, hypothesizing that NAC will normalize, and therefore reduce, levels of glutamate. We will measure glutathione levels with both MRS and serum levels, hypothesizing that NAC will increase glutathione levels in the brain and systemically. We will measure negative symptoms before, during and after treatment with NAC, hypothesizing an improvement in the NAC treatment group compared to placebo, based on findings in the literature. Finally, as an exploratory aim, we will measure performance on the MATRICS Consensus Cognitive Battery (MCCB), before and after NAC treatment, to test effects of NAC on cognition in schizophrenia.