  We present preliminary results on the variability properties of AGN above 20
keV in order to show the potential of the INTEGRAL IBIS/ISGRI and Swift/BAT
instruments for hard X-ray timing analysis of AGN. The 15-50 keV light curves
of 36 AGN observed by BAT during 5 years show significantly larger variations
when the blazar population is considered (average normalized excess variance =
0.25) with respect to the Seyfert one (average normalized excess variance =
0.09). The hard X-ray luminosity is found to be anti-correlated to the
variability amplitude in Seyfert galaxies and correlated to the black hole
mass, confirming previous findings obtained with different AGN hard X-ray
samples. We also present results on the Seyfert 1 galaxy IC 4329A, as an
example of spectral variability study with INTEGRAL/ISGRI data. The position of
the high-energy cut-off of this source is found to have varied during the
INTEGRAL observations, pointing to a change of temperature of the Comptonising
medium. For several bright Seyfert galaxies, a considerable amount of INTEGRAL
data have already been accumulated and are publicly available, allowing
detailed spectral variability studies at hard X-rays.
