  We present Bepposax observations of the starburst/Seyfert composite galaxy
Mrk609. This enigmatic object has an optical spectrum dominated by the features
of starburst galaxies, yet its X-ray luminosity (6.3$\times10^{42}$\lunits) is
typical of an AGN. The X-ray spectrum of Mrk609 can be parameterised by a
single power-law model with a photon index $\Gamma\sim1.6\pm0.1$ and no
evidence for significant absorption above the Galactic value. Long term
variability in both the 0.1-2 keV and 2-10 keV energy bands is detected, again
suggesting that the X-ray emission is dominated by an AGN. The observed broad
Ha component is a factor of 40 below that predicted by the
  X-ray flux implying a deficit of ionizing UV photons.
