We propose to obtain SWS spectra around the 3micron wavelength region
 with R~1700 for a sample of red dwarf stars.  The spectra will show
 strong features primarily due to photospheric water absorption; the
 stars have a range of effective temperature and metallicity and we
 will measure the dependence of the absorption features on these
 parameters.  We will analyse the data using our new state-of-the-art
 model atmospheres for M dwarfs, which include a detailed line-by-line
 treatment of water.  ISO observations of the water bands are crucial
 for increasing our knowledge of these cool, high-pressure, stellar
 atmospheres. Water vapour is thought to be the dominant opacity
 source in very low mass dwarf stars but it is extremely difficult to
 quantify from the Earth due to the presence of the terrestrial water
 bands.  ISO will allow us for the first time to determine the depth
 of the stellar water bands. Analysing the ISO spectrum using our new
 models will lead to vast improvements in our understanding of opacity
 sources, chemical composition, effective temperature, pressure and
 surface gravity for cool dwarf photospheres. This in turn will lead to
 much improved values for the fundamental parameters radius, luminosity
 and mass, for stars at the end of the main sequence.