  We present a multi-wavelength study (BVRI band photometry and HI line
interferometry) of nine late-type galaxies selected from the HIPASS Bright
Galaxy Catalog on the basis of apparently high HI mass-to-light ratios (3
M_sun/L_sun < M_HI/L_B < 27 M_sun/L_sun). We found that most of the original
estimates for M_HI/L_B based on available photographic magnitudes in the
literature were too high, and conclude that genuine high HI mass-to-light ratio
(>5 M_sun/L_sun) galaxies are rare in the Local Universe. Extreme high M_HI/L_B
galaxies like ESO215-G?009 appear to have formed only the minimum number of
stars necessary to maintain the stability of their HI disks, and could possibly
be used to constrain galaxy formation models. They may to have been forming
stars at a low, constant rate over their lifetimes. The best examples all have
highly extended HI disks, are spatially isolated, and have normal baryonic
content for their total masses but are deficent in stars. This suggests that
high M_HI/L_B galaxies are not lacking the baryons to create stars, but are
underluminous as they lack either the internal or external stimulation for more
extensive star formation.
