Forest fire is a major disturbance to the boreal ecosystem and may interact with climate change. Unfortunately, we have relatively little knowledge regarding fire activities in the boreal ecosystem. This study investigates the extent and dynamics of the forest fires occurred in and around the Boreal Ecosystem-Atmosphere Study (BOREAS) region during summer 1994, an active fire season on record. The statistics of fire activities were obtained from advanced very high resolution radiometer (AVHRR) (aboard NOAA 11) data employing two satellite-based remote sensing techniques that were designed particularly for monitoring boreal forest fires. Active fires and burned area are estimated using single-day images and 10-day clear composites. Such basic fire attributes as the area and period of burning extracted from the satellite data are compared against the ground reports made by the fire management agencies in Saskatchewan and Manitoba, Canada. Overall, there were 99 fires of a total burning area of approximately 2 million ha found over an area of 800¿700 km2 around the BOREAS study region in summer 1994. Agreement in the area of burning is good between the surface observations and satellite-based estimation using single-day images but poor using the composite data that suffer from various uncertainties. The majority (87%) of the ground-reported fires were detected by satellite; the satellite also identified some fires missed by the ground observers. Most fires in 1994 occurred in the transitional forest to the north and northwest of the BOREAS region. Regarding to the monitoring of fire evolution, the daily satellite detection approach can be as effective as or even more effective than ground observations, provided that cloud cover does not occur persistently. The smoke of the fires had an impact on some BOREAS flux measurements. ¿ 1997 American Geophysical Union