Deep infrared imaging surveys have revealed a class of faint galaxies which
 exhibit very red optical-to-IR colors (R-K>6).  Little is known about these
 mysterious objects due to their extreme optical faintness.  One exciting
 possibility is that these are galaxies with an evolved population of stars
 at high redshift.  If the red colors are due to the presence of an old
 stellar population, it requires a source redshift of about 2.  The existence of
 evolved galaxies at such a high redshift has profound implications for our
 understanding of galaxy formation and may place interesting constraints on the
 geometry of the Universe.  Alternatively, these red colors could be due to
 the presence of a highly reddened component present within galaxies at a more
 modest redshift.  This could be either a reddened AGN or a nuclear star burst.
 We request observations with the ISOCAM using the LW1 and LW2 bands to
 determine if these objects are old galaxies at high redshift or a new
 class of obscured AGN.  For the first scenario, ISOCAM colors will detect
 the characteristic roll over of the spectral energy distribution around
 4 microns (1.6 microns in the rest frame).  If instead they are a new class
 of reddened AGN, the spectral energy distributions should continue to rise
 from 2-8 microns.  Without ISO data it is not possible to extend the spectral
 energy distributions of these source to long enough wavelengths to test these
 models.