Light-curves are obtained for five irregular variables: one in M31 and four in M33. Observations extend continuously from 1916 to the present. Spectra are available for four of the five variables. The light-curves, color indices, and spectra show that a new class of variable star has been isolated. This class is characterized by (1) high luminosity, (2) blue color indices, and (3) intermediate F-type spectra. The absolute magnitude at maximum for these stars is a quantity of small dispersion. If in - M = 22.4 for M31 and in - M = 22.3 for M33, the observations give M (max.) = -6.9 + 0.2 (A.D.). If the provisional revision to the cosmic distance scale of M = -1.5, suggested by Baade, is adopted, these five variables have an absolute maguitude Mpg (max.) = -8.4 t 0.2 (A.D.). The small dispersion in this value shows the usefulness of this group of blue irregular variables as distance indicators. Additional stars of this type are known in other nebulae and provide a larger sample for future study.