A whole-body single-photon emission computed tomography system has been evaluated in terms of its physical performance. It consists of a standard GE 400 T maxi camera rotating on a ring stand, coupled to an Informatek Simis 3 computer system. In its standard mode of operation, 64 or 128 successive views of 64 X 64 or 128 X 64 matrices are collected at regular angular samples. The reconstruction of up to 64 possible adjacent transverse sections, sorted into coronal, sagittal, and oblique sections, is obtained by filtered backprojection. A conventional parallel-hole collimator is used. The uniformity of the camera field of view is corrected by the GE hardware module. The resolution in the transverse plane is typically of 15.5 mm in a 20 cm Lucite phantom, and independent of radial distance. The physical slice thickness is 19 mm (full width at half maximum of the longitudinal response using a point source) with only slight variations along the diameter of the image. The sensitivity is approximately 7,000 cps mCi-1 as measured using a 99m Tc thin source, enabling images of reasonable signal-to-noise ratio to be obtained in 10 min. The effect of the energy window, the number of angular samples, and the linear sampling modes on the transverse resolution and contrast is measured and discussed.