Schizophrenia and related psychoses are chronic brain disorders whose prognosis is often poor and whose pathophysiology remains obscure. Neuroimaging technologies such as PET (positron emission tomography), fMRI (functional magnetic resonance imaging), DTI (diffusion tensor imaging) and MRSI (magnetic resonance spectroscopic imaging) offer opportunities to elucidate the pathophysiology by studying brain function in living research subjects. The use of these techniques to study psychotic disorders is severely limited, however, by a critical methodological confound: antipsychotic treatment. The purpose of this protocol is to admit research subjects with schizophrenia and other related disorders to the Clinical Center, carefully evaluate their neuropsychiatric status, and discontinue psychotropic medications for a brief period so research subjects can be studied without the confound of antipsychotic treatment.