Outstanding progress in near-infrared detection technology and in real-time image processing has led astronomers to start undertaking all-sky surveys in the 1--2 mum range (project DENIS in Europe and 2MASS in the U.S.A.), surveys which will have a considerable impact in various areas of astronomy. This book gathers the contributions of more than 80 specialists involved in fields of interest as different as low mass stars, late stages of stellar evolution, star formation, stellar populations of the Galaxy and the Magellanic Clouds, the local structure of the Universe, and observational cosmology. It describes the impact on these fields of the exhaustive data bases and catalogs of