  Red supergiants (RSGs) are an evolved stage in the life of intermediate
massive stars (<25Mo). For many years their location in the H-R diagram was at
variance with the evolutionary models. Using the MARCS stellar atmosphere
models, we have determined new effective temperatures and bolometric
luminosities for RSGs in the Milky Way, LMC, and SMC, and our work has resulted
in much better agreement with the evolutionary models. We have also found
evidence of significant visual extinction due to circumstellar dust. Although
in the Milky Way the RSGs contribute only a small fraction (<1%) of the dust to
the interstellar medium (ISM), in starburst galaxies or galaxies at large
look-back times, we expect that RSGs may be the main dust source. We are in the
process of extending this work now to RSGs of higher and lower metallicities
using the galaxies M31 and WLM.
