Within the tropics, due to high cloud cover, vegetation monitoring can only be achieved by using both visible and microwave spaceborne data. In the present study, Shuttle Imaging Radar (SIR-B) data and SPOT data acquired over central Sumatra are used in a supervised classification of vegetation. Emphasis is put on SAR data utilization. Assessment of SAR data potentialities is carried out by using (1) SIR-B imagery alone, and (2) combined SJR-B and SPOT data. The article describes the methodology developed for exploiting the SIR-B image including raw data analysis, image filtering and image classification. Finally, combined filtered SIR-B imagery and SPOT data are used jointly in a supervised classification leading to a better discrimination of surface units. These results indicate the unique capabilities of combined visible and SAR data for monitoring tropical vegetation, especially for forest/non-forest discrimination.