Four-color observations of field horizontal-branch stars.

In this review paper the method of detecting FHB stars in the galactic halo is discussed. The similarity of FHB stars to blue horizontal-branch stars in globular clusters is outlined and then followed by a discussion of the characteristics of some of the brightest FHB stars. The distribution of the points representing HB stars in the various four-color, and related, diagrams allow some conclusions to be drawn about the nature of stars on the horizontal-branch.