  Most of the local active galactic nucleus (AGN) population is obscured and
much of the X-ray background originates in obscured AGNs. The contribution of
obscured accretion to the growth of massive black holes is discussed here. The
recent identification of significant samples of the X-ray sources that dominate
the X-ray background intensity has shown a redshift peak at 0.7-0.8, rather
than the redshift of 2 found for bright optical quasars. Obscured accretion has
a faster evolution than unobscured accretion. The lower redshift and luminosity
of most obscured AGNs mean that although they dominate the absorption-corrected
intensity of the X-ray background by a factor of about 3 over unobscured
objects, they make only an equal contribution to the local mass density in
black holes. Obscured and unobscured AGNs together contribute about 4 x 10^5
Msun/Mpc^3. Type 2 quasars and Compton-thick objects may give another 10^5
Msun/Mpc^3, but no more unless direct determinations from the M-sigma relation
seriously underestimate the local black hole mass density, or unless most
massive black holes are rapidly spinning (so having a higher radiative
efficiency than the 10% assumed above). Obscured accretion probably dominates
the growth of black holes with masses below a few times 10^8 Msun, whereas
optically bright quasars dominate at higher masses. The luminosity absorbed by
the dusty gas in obscured AGNs is reradiated in the mid-infrared and
far-infrared bands. The contribution of AGNs drops from about 20% of the
mid-infrared background to just a few percent of the far-infrared background.
