  We discuss dynamical mass measurements of high-z galaxies with the Next
Generation Space Telescope (NGST). In particular, we review some of the
observational limits with the current instrument/telescope generation, we
discuss the redshift limits and caveats for absorption and emission lines
studies with NGST, and the existence of suitable targets at high redshift. We
also briefly summarize strengths and weaknesses of proposed NGST instruments
for dynamical studies.
