[en] SPECT is currently in a state of evolution. Improvements are being made in camera detectors, flood nonuniformity correction, and algorithms to correct for attentuation and scatter. New algorithms for image reconstruction and filtration that reduce statistical noise are under development. SPECT is a more complicated modality than planar scintigraphy, and to obtain maximum diagnostic information requires special expertise on the part of the physicians and technologists who employ its use. The performance of systems is improving. The findings reported in this review reflect the current technology at this time. Although the numbers of papers and abstracts concerning SPECT in the literature are large, these data do not necessarily reflect a large clinical experience, since most of the studies cited have had relatively few number of patients. One should therefore view SPECT as a very powerful tool whose potential utility is only beginning to be appreciated. New radiopharmaceuticals labeled with /sup 99m/Tc that will permit imaging of myocardial and brain-blood flow are under development. The impact of these and other new radiotracers, such as labeled antibodies, can be expected to impact on the future use of emission computed tomography