Room-temperature infrared luminescence with high quantum yield (48%) has been observed from HgTe nanocrystals. The colloidal preparation, reported for the first time, gave rise to nanocrystals of size 3 to 6 nm with coloradoite structure. The thiol-capped quantum dots. precipitated as a white powder from the colloidal solution with 2-propanol, and readily redissolved in water, are stable towards oxidation and display luminescence covering the 1.3 mu m telecommunications fiber window.