  Observations and interpretation of extragalactic rotational and rovibrational
H2 emission are reviewed. Direct observations of H2 lines do not trace bulk H2
mass, but excitation rate. As such, the H2 lines are unique diagnostics, if the
excitation mechanism can be determined, which generally requires high-quality
spectroscopy and suitable additional data. The diagnostic power of the H2 lines
is illustrated by two cases studies: H2 purely rotational line emission from
the disk of the nearby spiral galaxy NGC891 and high resolution imaging and
spectroscopy of H2 vibrational line emision from the luminous merger NGC6240.
