One of the possible applications of satellite radar remote sensing is to estimate surface soil moisture. To evaluate the capacity of ERS 1/synthetic aperture radar (SAR), a European Space Agency (ESA) pilot project has been set up. The test site is a small agricultural watershed situated in the central part of French Brittany. During 1992 and 1993, almost all possible SAR images were acquired together with two types of ground truths: intensive ground measurements during 14 field campaigns and point automatic measurements over the entire period. From the comparison of those ground truth data with the ERS 1 images, the following results are obtained. On a field scale the relation between the radar signal and the surface soil moisture depends strongly on the type of culture: Correlation is poor for the different cultures except for wheat. On a basic scale, it is shown that during the period of low vegetation density, there is a linear correlation between the mean radar data and the point automatic measurements. This last result is very encouraging and could open the way to hydrological applications. ¿ American Geophysical Union 1995