Abstract. This paper presents initial tests of a novel and relatively simple methodology for near real-time operational detection of deforestation in Amazonia. Channel 3 (3.7mum) full resolution (1.1km) and geometrically corrected images of the Advanced Very High Resolution Radiometer (AVHRR) on-board the NOAAseries satellites covering the same region on different dates are digitally compared. Differences in forest cover between pairs of images are automatically selected as potential deforestation sites. In the tests, three AVHRR images (September 1989 and 1990; July 1990) were compared with 30 m high-resolution Landsat Thematic Mapper (TM) data using a geographical information system (GIS) integrated to the image processing. The percentages of correct location of newly deforested sites for September 1989-1990 and September 1990-July 1990 comparisons were, respectively: 49.1 and 56.5 per cent for about 200 deforestation sites of assorted sizes, and 82 and 90 per cent for sites larger than 3.1 km 2.