  Infrared observations of complete samples of active galactic nuclei (AGN)
have shown that a substantial fraction of their bolometric luminosity is
emitted at wavelengths ~8-1000microns. In radio-loud and Blazar-like objects
much of this emission appears to be direct non-thermal synchrotron radiation.
However, in the much larger numbers of radio-quiet AGN it is now clear that
thermal dust emission is responsible for the bulk of radiation from the
near-infrared through submillimeter wavelengths. Luminous infrared-selected AGN
are often surrounded by powerful nuclear starbursts, both of which appear to be
fueled by enormous supplies of molecular gas and dust funneled into the nuclear
region during the strong interaction/merger of gas rich disks. All-sky surveys
in the infrared show that luminous infrared AGN are at least as numerous as
optically-selected AGN of comparable bolometric luminosity, suggesting that AGN
may spend a substantial fraction of their lifetime in a dust-enshrouded phase.
The space density of luminous infrared AGN at high redshift may be sufficient
to account for much of the X-Ray background, and for a substantial fraction of
the far-infrared background as well. These objects plausibly represent a major
epoch in the formation of spheroids and massive black holes (MBH).
