The HR Diagram and the Galactic Distance Scale After Hipparcos

The completion and publication of the Hipparcos astrometric catalogue has revitalized studies in many fundamental areas of Galactic structure and stellar evolution. This article reviews the impact of the new parallax results on our understanding of the location of the main-sequence as a function of abundance, of the luminosity calibration of primary distance indicators and of the Galactic distance scale. Many of these issues remain to be resolved.