  The importance of the Atacama Large Millimeter Array (ALMA) to the study of
high-redshift dusty gas-rich galaxies is described. ALMA will have dramatically
greater sensitivity and angular resolution than existing millimetre(mm) and
submm-wave telescopes. Two key areas are emphasized: i) extremely deep galaxy
surveys down to flux densities of about 10 microJy, two orders of magnitude
deeper than can be reached using existing telescopes; ii) the study of known
high-redshift galaxies, quasars and gravitational lenses. The sensitivity of
ALMA will allow very faint galaxies to be detected, while its angular resolving
power avoids the problem of source confusion. Dust continuum emission,
molecular rotational line emission and atomic fine-structure line emission will
all be detected from high-redshift galaxies. Both the spatial structure of
continuum emission and the spatial and velocity structure of line emission will
be resolved, revealing the astrophysical processes at work in detail. These
programs are very complementary to surveys using the Next Generation Space
Telescope (NGST) and Planck Surveyor.
