The monitoring of soil moisture (SM) can be performed through remote sensing technologies. Among the operational microwave radiometers potentially able to provide information about SM and its variability in the space-time domain, in this work the capability of the AMSU (Advanced Microwave Sounding Unit) sensor has been investigated. In particular, SM information, achieved implementing two different AMSU-based indices, has been compared with both in situ measured and modeled observations for several sites spread out all over Italy. The results indicate that the AMSU sensor can be considered as a useful tool to provide quite reliable information about SM variability, mainly if its high temporal resolution is taken into account.