The charcoal content of surface and late-Quaternary lake sediments in boreal forests of northcentral Alaska was investigated using an image-analysis procedure that tallied and measured the area of charcoal particles in size classes. Modern sediments were from mud-water interfaces of 29 lakes within watersheds assigned to 3 categories (unburned, partially burned, and extensively burned) based on extent of the watersheds burned in fires during 1986 and 1990. Lakes in extensively burned drainages generally contained more charcoal than did lakes in partially burned or unburned drainages, but charcoal content of sediments varied greatly within categories. Charcoal accumulation rates in a sediment core from Sithylemenkat Lake ranged between c. 1000 and 5000 μm2 cm-2 yr-1 over the past 14,000 yr. Lowest rates occurred between c. 7000 and 5000 yr BP, after the establishment of boreal forest and during a period of abundant alder shrubs. In general, the great variability in particle sizes encountered in the modern and fossil samples from Alaskan boreal forests and the large number of particles needed to characterize trends in individual size classes suggest that an automated measurement approach, such as image analysis, is needed for quantifying sediment charcoal.