This book contains a selection of refereed papers presented at the 6 Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment held in Florence, Italy on March 15-18, 1999. Over the last two decades, passive microwave remote sensing has made considerable progress, and has achieved significant results in the study of the Earth's surface and atmosphere. Many years of observations with ground-based and satellite-borne sensors have made an important contribution to improving our knowledge of many geophysical processes of the Earth's environment and of global changes. The evolution in microwave radiometers aboard satellites has increased steadily over recent years. At the same time, many investigations have been carried out both to improve the algorithms for the retrieval of geophysical parameters and to develop new technologies. The book is divided into four main sections: three of these are devoted to the observation of the Earth's surface and atmosphere, and the fourth, to future missions and new technologies. The first section deals with the study of sea and land surfaces, and reports recent advances in remote sensing of ocean wind, sea ice, soil moisture and vegetation biomass, including electromagnetic modelling and the assimilation of radiometric data in models of land surface processes. The following two sections are devoted to the measurement of atmospheric quantities which are of fundamental importance in climatology and meteorology, and, since they influence radio-wave propagation, they also impact on several other fields, including geodesy, navigational satellite and radioastronomy. The last section presents an overview of new technologies and plans for future missions.