Mercury-cadmium telluride (HgCdTe or Hg1-xCdxTe) has emerged over the past fifteen years as the most widely applicable infrared quantum detecor material available today. Highly sensitive photoconductors, photodiodes and MIS (metal-insulator-semiconductor) detectors, achieving in many cases background-limited performance, are now being used in or being developed for a wide range of DoD and NASA sensor applications over the 2-30 micrometer spectral range. This paper is a brief review of the basic principles of operation, the performance characteristics, and the state-of-the-art of HgCdTe infrared detectors. Emphasis is placed on HgCdTe photoconduc-tors and photodiodes. The paper is intended to provide basic information to those who are or who will be incorporating HgCdTe detectors into modern infrared sensors and systems.