In a subtropical region, the application of remote sensing in geological survey and mapping is limited by the dense vegetation and soil cover and poor data availability due to clouds and rain. This study emphasizes the detection of structural and lithological features underneath a vegetation canopy using shuttle imaging radar C/X band synthetic aperture radar (SIR-C/X-SAR) data. Zhao Qing test site in southern China was selected for this study. The SIR-C/X-SAR data have advantages including all weather, all time imaging capability, high altitude, and wide swath along with the expanded information from multifrequency and multipolarization that improves the geological interpretibility, especially in a moist, vegetated region. This paper presents interpretations of structures, beds, and lithostratigraphic units from the shuttle imaging radar data, and makes an assessment of SIR-C/X-SAR data for geological mapping. ¿ American Geophysical Union 1996