Biomass burning releases significant amounts of trace gases and smoke aerosol into the atmosphere. This has an impact on the Earth's radiation budget, the magnitude of which has not yet been well quantified. Satellite remote sensing is well suited to assessing the area of biomass burning, a prerequisite for estimating emissions at regional and global scales. Commonly used satellite-based techniques for measuring burned areas include thermal hotspot detection and multitemporal NDVI analysis, each having several limitations. Here we present a new, hybrid approach for boreal burned area mapping called HANDS, or hotspot and NDVI differencing synergy. The automated technique was tested using satellite data covering Canada for the 1995 and 1996 fire seasons, and comparing results with official burned area statistics and conventional fire surveys. HANDS computed a national burned forest area of 6.8 million ha in 1995 and 2.0 million ha in 1996, corresponding favorably to Canadian Forest Service estimates of 7.1 million ha and 1.9 million ha, respectively. Moreover, in most cases, the technique accurately delineated the boundaries of individual burns and identified some burns that were missed with conventional mapping. When employed in conjunction with NOAA-AVHRR imagery, HANDS provides a consistent means of mapping large burns (>10 km2), which are characteristic for the boreal forest. New generation sensors (e.g., SPOT VEGETATION, Terra MODIS) should enable its successful application to a wider range of environments.