The HST Key Project on the Extragalactic Distance Scale: A Search for Three Number.- Calibration of the Distance Scale From Cepheids.- Currents Uncertainties in the Use of Cepheids as Distance Indicators.- The Cepheid Calibration of Type Ia Supernovae as Standard Candles.- RR Lyrae Distance Scale: Theory and Observations.- Globular Cluster Distances From RR Lyrae Stars.- Blue Supergiants as a Tool For Extragalactic Distance - Theoretical Concepts.- Blue Supergiants as a Tool for Extragalactic Distances - Empirical Diagnostics.- Supernovae as Cosmological Standard Candles.- Type Ia -Supernovae and Cosmology Models for Type Ia Supernovae and Cosmology.- Novae as Distance Indicators.- Extragalactic Distances from Planetary Nebulae.- Distances to Local Group Galaxies.- The Globular Cluster Luminosity Function: New Progress in Understanding an Old Distance Indicator.