  We present a cross-correlation of the European Large Area ISO survey (ELAIS)
with the ELAIS Deep X-ray Survey of the N1 and N2 fields. There are 7 Chandra
point sources with matches in the ELAIS Final Analysis 15um catalogue, out of a
total of 28 extragalactic ISO sources present in the Chandra fields. Five of
these are consistent with AGN giving an AGN fraction of ~19 per cent in the
15um flux range 0.8-6 mJy. We have co-added the hard X-ray fluxes of the
individually-undetected ISO sources and find a low significance detection
consistent with star formation in the remaining population. We combine our
point source cross-correlation fraction with the XMM-Newton observations of the
Lockman Hole and Chandra observations of the Hubble Deep Field North to
constrain source count models of the mid-infrared galaxy population. The low
dust-enshrouded AGN fraction in ELAIS implied by the number of
cross-identifications between the ELAIS mid-infrared sample and the Chandra
point sources is encouraging for the use of mid-infrared surveys to constrain
the cosmic star formation history, provided there are not further large
undetected populations of Compton-thick AGN.
