A comparison of the soil moisture response of three 1–4  GHz radiometers from truck and aircraft platforms at a variety of lest sites indicates that microwave remote sensing of bare soil produces repeatable and quantifiable results regardless of geographic location and sensor system used. The combined microwave sensitivity of these data sets appears to be of the order of − 3–4deg K per 1 per cent change in volumetric soil moisture for L-band wavelengths ( − 2–7 deg K per 1 per cent soil moisture if watersheds characterized by vegetation and surface roughness are included). With the addition of appropriate algorithms to handle the effect of roughness and vegetation, these results demonstrate the potential of microwave remote sensing for estimating soil moisture over large areas.