The high thermal conductivity and low thermal expansion of silicon carbide make it an ideal mirror material for synchrotron radiation applications. Such mirrors must withstand absorption of a few kilowatts of x-ray flux without degradation or distortion. Silicon carbide has the added advantage of high reflectance in the vacuum UV. Many different polycrystalline forms of silicon carbide are available. The fabrication of mirrors in hot pressed, reaction bonded and chemical vapour deposited (CVD) silicon carbide is described, from manufacture of the initial blanks, through diamond grinding of the optical figure, to final polishing and installation in the synchrotron. The suitability of each of these materials as mirror substrates has been assessed from the point of view of crystal structure, polishability, optical figure stability, reflectance and vacuum compatibility. Chemical vapour deposited silicon carbide gives an excellent optical finish, the best polished sample produced so far having a reflectance three times that of gold at 584 R, but it is difficult to make in large flat pieces. The hot pressed and reaction bonded materials are much more easily obtainable and take a good enough polish for most applications. Several flat, spherical and cylindrical mirrors in CVD, hot pressed and reaction bonded silicon carbide are planned or have been in use as premirrors in the Synchrotron Radiation Source (SRS) at Daresbury. Their performance during machine operation and the future availability of silicon carbide mirrors is discussed.