This technical protocol describes the procedural aspects of [I-123]IBZM SPECT. It is not intended to be sufficient on its own for a clinical study. All subjects volunteering for this study will be recruited from among individuals who have previously consented to participate in clinical studies under one of two NIH protocols that include genetic testing. Schizophrenia patients will be recruited from among NIMH inpatients participating under NIH protocol #89-M-0160, "Inpatient Evaluation of Neuropsychiatric Patients" (Egan 1999a). Normal volunteers will be recruited from among those participating under NIH protocol #95-M-0150, "A Neurobiological Investigation of Patients with Schizophrenia Spectrum Disorders and Their Siblings" (Egan 1999b), which includes recruitment of a normal control group whose first degree relatives are free of mental illness. All details related to clinical care and genetic analysis are contained in those two protocols and their associated consent forms; all details related to [I-123]IBZM SPECT studies, per se, are discussed in this protocol, which requires a separate informed consent from each volunteer.