Relationships among fire characteristics, fire damage, tree mortality, and sucker response in Populustremuloides Michx. are described. Circumference charred averaged more than 75% on trees killed and less than 50% on live trees. Average char heights ranged from 0.5 m in low severity fire to 1.5 m in high severity fire. Logistic regression analysis showed that probability of mortality was strongly related to diameter at breast height (dbh), char height, and circumference charred. Char heights of 30 cm had a 90% probability of killing aspen less than 25 cm dbh. Bark thickness at breast height and 10 cm aboveground, which relates to fire resistance, related strongly to tree dbh. Bark thickness was the same at sidehill, downhill, and uphill positions. Minimal flame heights required to kill aspen with 90% probability ranged from 10 cm for a 10-cm dbh tree to 60 cm for a 25-cm dbh tree. Number of suckers per hectare on three burns varied from 9 880 to 57 570 the 1st year following fire and from 7 060 to 21 240 4 years after the fire. Depth of sucker origin ranged from 0.2 to 18 cm and was related to fire severity. Sucker density varied greatly between plots and was not significantly related to fire severity.