  The FIRBACK project is a collaboration of eight institutes aimed at using
long wavelength surveys with ISO to uncover the nature of the Cosmic
Far-Infrared Background. We have surveyed nearly 4 sq. deg. in three regions in
the northern and southern hemispheres with the ISOPHOT instrument on ISO, using
the 175 micron filter. As reported by Puget et al. (1998) and Reach et al.
(these proceedings), the first 0.25 sq. deg. region studied in this programme
contains many more 175 micron sources than expected. Initial reduction of the
remaining survey areas appears to confirm this result. The area surveyed by
FIRBACK represents the largest and deepest long wavelength far-IR survey
available before the launch of SIRTF.
