The performance characteristics of Frisch-ring CdZnTe (CZT) detectors are described and compared with other types of CZT devices. The Frisch-ring detector is a bar-shaped CZT crystal with a geometrical aspect ratio of /spl sim/1:2. The side surfaces of the detector are coated with an insulating layer followed by a metal layer deposited directly upon the insulator. The simple design operates as a single-carrier device. Despite the simplicity of this approach, its performance depends on many factors that are still not fully understood. We describe results of testing several detectors fabricated from CZT material produced by different vendors and compare the results with numerical simulations of these devices.