  The XMM-Newton observatory has the largest collecting area flown so far for
an X-ray imaging system, resulting in a very high sensitivity over a broad
spectral range. In order to exploit fully these performances, a very accurate
calibration of the XMM-Newton instruments is required, and has led to an
extensive ground and flight calibration program. We report here on the current
status of the EPIC/MOS cameras calibrations, highlighting areas for which a
reasonably good accuracy has been achieved, and noting points where further
work is needed.
