In a May 1972 study in central Alberta, 13 0.5 ha plots of semimature trembling aspen were burned experimentally under various conditions to provide new information on fire behaviour and impact, with particular regard to aspen ecosystems. Fire data were documented for all plots, particularly head fire rates of spread and frontal fire intensities. The following August an assessment was made of the impact of burning on aspen overstory mortality and understory vegetation response. In May 1978 two of the plots were jointly reburned. The August survey that followed assessed the effects of the reburning.