Single photon emission computed tomography (SPECT) has become an invaluable tool in medicine. A program is proposed for the design and evaluation of a novel high sensitivity, high resolution SPECT instrument. The energy and spatial resolutions of the proposed detector is expected to be greater, by about a factor of 2, than current systems. The high angular resolution and wide aperture enables detailed imaging of large organs. Good energy resolution will improve discrimination against natural and scattered gamma ray background beyond current systems. Improved sensitivity by a factor of about 100 permits faster (10 to 30 secs) dynamic imaging. The detector can be designed to image the body or the brain without the need for rotation. The proposed instrument is expected to be substantially smaller and lighter than Anger cameras. It also has good potential to be used for medical diagnosis in the field. Phase I results demonstrate the potential of the proposed SPECT. A fully functional engineering prototype single head SPECT instrument will be developed during Phase II to demonstrate the capability of the proposed technique. During Phase III a commercial SPECT instrument will be built.