We propose to carry out a systematic investigation of the FIR
 properties of a sample of 17 of the most luminous FIR objects known,
 16 of which have FIR luminosties greater than 10^13 Lsol. These form
 the largest sample of hyperluminous objects known. Moreover, this is
 the only large sample at truly cosmological distances for which IRAS
 has already shown that there is prodigious quantities of dust. It is
 therefore an ideal sample for detailed study of dust, at a redshift
 of order unity.

        We will use the ISO observations of these objects to determine
 the mass and characteristic temperature of the dust.  This will allow
 us to study the interplay between star formation and AGN activity
 within young and possibly forming objects.  For instance, if the
 spectral energy distribution is charactised by predominantly cooler
 dust(ie <100K), this supports a predominantly star burst origin for
 the dust emission whereas if the dust is warmer an AGN origin for the
 energy input is more likely. Apart from their relatively high redshift
 these objects are an important sample to study, purely on the basis of
 their high FIR luminosity.

        Studying this sample with a median redshift of order 1 is of
 crucial importance since this will allow us to compare the dust
 properties of these objects, with the more thoroughly studied objects
 at low redshift (ie z=0.1) and with the equally important but very
 difficult to study objects which ISO will study in the redshift range
 3 to 5.

        The ISO observations will also be a fundamental ingredient in
 our ongoing program of multi-wavelength observations of this class FIR
 selected objects from the radio to the hard X-rays.