We propose to make ISOCAM and ISOPHOT observations  of candidate high-redhift
luminous  infrared galaxies  selected from  the  IRAS  Faint Source  Database.
The prototype, IRAS F10214+4724 at z=2.286, implying  L_ir ~  10^14  L_sun and
M_H2 ~ 10^11M_sun, is  the most infrared-luminous  and gas-rich  object known.
It  may be the  first discovered, long  sought,  protogalaxy, although it also
has some  quasar-like  properties.  We have selected   faint   (S_60 < 0.3Jy),
high S_ir/S_optical (nu*S_60/nu*S_blue > 30) extragalactic sources in the FSDB
using the  IRAS  OptID database.  The   majority of  these   are blank optical
fields (b > 21) from digitized (COSMOS) survey plate data of the southern sky.
The well-established correlation between  IR/Optical ratio and FIR  luminosity
translates the above  selection into   high luminosity  (L_ir  >  10^12L_sun),
which, combined  with  the S_60 limit,  selects  for high-redshift (z  > 0.3).
Our sample is the  result of the best possible  systematic  search through the
entire all-sky IRAS database for the deepest (infrared) and faintest (optical)
fields (using the high quality SERC/UKSTU survey  plates), and thus represents
the best all-sky sample for cosmology.  ISOCAM images  at  12um will determine
accurate    positions  for    these  sources    and  allow  positive   optical
identification.  Combined with ISOPHOT measures at 90um and 180um and existing
IRAS 60um flux-densities,   these will determine  the infrared spectral-energy
distributions, infrared luminosities and dust masses for a sample of 98 of the
best candidates.