By summarizing and analyzing some related papers published in English over the last few years, the status of third generation Mercury Cadmium Tellurium (MCT) devices, including two-colour or three-colour detectors with novel device structure, avalanche photodiodes and multi-spectral arrays, were presented. The developments of third generation MCT devices in array size, very long wavelength application of photovoltaic technology, multi-colour, readout capability and etc were analyzed. It is pointed that the sophisticated controllable vapor phase epitaxial growth methods, such as Molecular Beam Epitaxy (MBE) and metal organic chemical vapour deposition (MOCVD), can be used to fabricate almost ideally designed heterojunction photodiodes. With the progress of MCT technology based on MBE, large wafers (4 inches and more) are available on germanium in France and on silicon in the USA. This enables larger wafer to have a sensitive thin film deposition, of which the thickness is controllable. Third generation MCT technology is hopeful of achieving the high-rate production in three or five years according to the related progress right now.