This database table is based upon the information contained in the Catalog of Galactic O-Type Stars (Garmany, Conti, and Chiosi 1982), which is a compilation from the literature of all O-type stars for which spectral types, luminosity classes, and UBV photometry exist. Most of the entries come from Cruz-Gonzalez, et al. (1974) and Humphreys (1978), with additional stars from Garrison and Kormendy (1976); Garrison, Hiltner, and Schild (1977); Garrison and Schild (1979); Feinstein, Marraco, and Muzzio (1973); Feinstein, Marraco, and Forte (1976); and Moffat, Fitzgerald, and Jackson (1979). As discussed below, the HEASARC has deleted 5 of the original 765 entries which we believe to be erroneous and/or redundant, and modified the names and/or positions of 14 other entries. As part of the checking process, the HEASARC created new, more accurate positions for all the entries using the SIMBAD database. The catalog contains 760 stars, for each of which designations (HD, DM, etc.), spectral types, V magnitudes, B-V magnitudes, cluster memberships, positional information, and source references are given. In addition, the authors have included derived values of absolute visual and bolometric magnitudes, and distances. The source reference should be consulted for additional details concerning the derived quantities. This is a service provided by NASA HEASARC .