Soil moisture plays a crucial role in hydrology, agronomy, and meteorology. It governs the redistribution of precipitation between infiltration and runoff, it affects the development of crops through its dominance on regulating water uptake by plants, and it manages the partitioning of energy and water through evaporation and transpiration at the lower boundary of the atmosphere. Monitoring soil moisture status on regional and global scales is of primary importance for understanding and protecting our environment, as well as for management of natural resources as emphasized by the World Climate Research Program. Microwave radiometry is the most successful of the remote sensing approaches for sensing soil moisture. Microwave radiometry, or passive microwave remote sensing, is one of the radio-physical methods used for remote observations of the environment. It is based on measurements of the natural electromagnetic radiation of the environmental objects like land, water, snow, ice, and the atmosphere in the millimeter to decimeter wavelength range. Investigations of water and land surfaces are taking place in the 0.5 to 50 cm band of electromagnetic wavelengths, in practice, in between 2 and 3 cm (X-band), 5 and 6 cm (C-band), and 18 and 30 cm (L-band). Inside these bands, the land surface radiation is primarily a function of the free water content in soil but is also influenced by other parameters, such as depth to a shallow water table (L-band) and vegetation biomass (X- and C-band). The fundamentals of this approach are well established and surface soil moisture retrieval algorithms have been verified using ground based experiments and aircraft observations. This presentation will provide results of microwave radiometric experiments conducted during 2002 through 2005 at the test sites of the Center for Hydrology, Soil Climatology and Remote Sensing (HSCaRS), Alabama A&M University by an international team of scientists from the United States of America (USA) and Russian. The microwave measurements were conducted from ground locations using a mobile (rover) platform and unmanned helicopter (aerial) platform. The data were collected using microwave radiometers which are portable light weight devices operating at the wavelengths of 6 cm, 18 cm, and 21 cm that were provided by the Institute of Radioengineering and Electronics (IRE), Russian Academy of Sciences (RAS). Discussion will be made of the “radiation vs soil moisture” data as well as of the accuracy of soil moisture microwave assessments.