  Massive low surface brightness galaxies have disk central surface
brightnesses at least one magnitude fainter than the night sky, but total
magnitudes and masses that show they are among the largest galaxies known. Like
all low surface brightness (LSB) galaxies, massive LSB galaxies are often in
the midst of star formation yet their stellar light has remained diffuse,
raising the question of how star formation is proceeding within these systems.
HI observations have played a crucial role in studying LSB galaxies as they are
typically extremely gas rich. In the past few years we have more than
quadrupled the total number of massive LSB galaxies,primarily through HI
surveys. To clarify their structural parameters and stellar and gas content, we
have undertaken a multi-wavelength study of these enigmatic systems. The
results of this study, which includes HI, CO, optical, near UV, and far UV
images of the galaxies, will provide the most in depth study done to date of
how, when, and where star formation proceeds within this unique subset of the
galaxy population.
