A typical SPECT system consists of a single or multiple units of radiation detectors arranged in a specific geometric configuration and a mechanism for moving the radiation detector(s) or specially designed collimators to acquire data from different projection views. In general, SPECT instrumentation can be divided into three general categories (1) arrays of multiple scintillation detectors, (2) one or more scintillation cameras, and (3) hybrid scintillation detectors combining the first two approaches. In addition, special collimator designs have been proposed for SPECT for specific purposes and clinical applications. The following is a brief review of these SPECT systems and special collimators.