  This review briefly summarizes our knowledge of the X-ray emission from
single WN, WC, and WO stars. These stars have relatively modest X-ray
luminosities, typically not exceeding L_sun. The analysis of X-ray spectra
usually reveals thermal plasma with temperatures reaching a few 10 MK. X-ray
variability is detected in some WN stars. At present we don't fully understand
how X-ray radiation in produced in WR stars, albeit there are some promising
research avenues, such as the presence of CIRs in the winds of some stars. To
fully understand WR stars we need to unravel mechanisms of X-ray production in
their winds.
