  We present results of a timing analysis of various isolated pulsars using
ESA's \emph{XMM-Newton} observatory. Isolated pulsars are useful for
calibration purposes because of their stable emission. We have analyzed six
pulsars with different pulse profiles in a range of periods between 15 and 200
ms. All observations were made using the \emph{EPIC-pn camera} in its faster
modes (Small window, Timing and Burst modes). We investigate the relative
timing accuracy of the camera by comparing the pulse periods determined from
the \emph{EPIC-pn camera} observations with those from radio observations. As a
result of our analysis we conclude that the relative timing accuracy of the
\emph{EPIC-pn camera} is of the order of $1\times 10^{-8}$.
